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Having a % Chance of Being Successful at "X", is a very natural way of explaining things.

Why haven't Percentile-Based Systems won out in a big way, in the RPG market?

Thanks in advance, for chiming in.

Quote from: Jam The MF on July 15, 2022, 07:13:11 PM
Having a % Chance of Being Successful at "X", is a very natural way of explaining things.

Why haven't Percentile-Based Systems won out in a big way, in the RPG market?

There are successful percentile systems, notably Call of Cthulhu, which is one of the most popular RPGs of all time. So there's nothing wrong with percentile systems, but I don't think they are seen as markedly superior.

1) Explaining the odds isn't a primary mark of success in a game in general. Few games outside of RPGs use percentile dice either (i.e. wargames, board games, dice games).

2) Bigger numbers mean more difficult math. Adding and subtracting numbers from 1 to 10 or so can be done easily, but it gets harder the larger one goes.

3) Percentile stats make it difficult to express large differences like in high-power fantasy or superheroes, because values higher than 100% are counter-intuitive.

Quote from: jhkim on July 15, 2022, 07:30:50 PM

Quote from: Jam The MF on July 15, 2022, 07:13:11 PM
Having a % Chance of Being Successful at "X", is a very natural way of explaining things.

Why haven't Percentile-Based Systems won out in a big way, in the RPG market?

There are successful percentile systems, notably Call of Cthulhu, which is one of the most popular RPGs of all time. So there's nothing wrong with percentile systems, but I don't think they are seen as markedly superior.

1) Explaining the odds isn't a primary mark of success in a game in general. Few games outside of RPGs use percentile dice either (i.e. wargames, board games, dice games).

2) Bigger numbers mean more difficult math. Adding and subtracting numbers from 1 to 10 or so can be done easily, but it gets harder the larger one goes.

3) Percentile stats make it difficult to express large differences like in high-power fantasy or superheroes, because values higher than 100% are counter-intuitive.

^This, plus having X% chance to succeed isn't that natural when you're rolling against an opposed ability or a certain difficulty that varies by circumstance. In which case you may have to resort to math that would mess up your neatly predetermined % of success.

It's subjective, but I also think that a single d20 roll has a better feel than either two d10s or a single clunky as hell d100 roll. And % values in most systems tend be divisible by 5 anyways, and 100/5 = 20. So if you're (usually) going to be rolling in increments of 5% anyways, you might as well go for a die that's already divided in 5% increments, i.e. the d20 (the most popular die type IMO).

Also, I don't think non-nerds think in percentages, so basing a system around them makes it accessible only for a certain subset of the player base, specially now that RPGs are for cool kids too, not just math geeks.

Because I want to actually use all the goddamn nice I paid for. That may not be the most common answer to the question. But it's probably the best answer. And maybe even the most honest answer.

Personally, I'm very pro d100. At the end of the day, probability is most naturally expressed as a percentage.

However, there is a pecking order of what feels "organic."

A 1 in 3 chance to bash down doors seems like a good, off-the-cuff estimate. Like if you were a journalist traveling through time and alternate dimensions to the fantasy world where a party is actually in a dungeon bashing down doors, and you catch the barbarian in a rare idle moment where he's scratching his ass because his hireling used too much starch on his loin cloth again, and if you went up and asked him, "How many doors would you say you bust open on the first try?" "About 1 in 3" seems like an answer you might genuinely get.

You can ham-fist it into a d20. 7 in 20 chance. Okay, it's not exactly the same. But close enough. Graininess or some such gamer jargon bullshit. And the gamer might even argue, "well *snort* ackchyually, we don't know what the exact probability is because it got truncated to the graininess of the d6. Technically, since d20 is higher resolution, 7 in 20 is likely more accurate."

And yet 7 in 20 just doesn't seem to vibe as nicely as 1 in 3. And maybe it has something to do with wanting to imagine Thorgar of the Itchy Jock rather than Milton, the kid from school who used to get beat up for his milk money.

Percentile, in my estimate, is at the middle of the pecking order. It feels less organic than "1 in 3" but a hell of a lot more organic than "7 in 20." Even though on some level it's just the latter on steriods--33 in 100--because percent is a part of our natural language, it vibes a lot better.


Near as I can tell, the evolution of game mechanics went something like this. You originally started with two game mechanics.
1) Decide on a reasonable probability, and roll whatever dice is convenient.
2) Cross-reference the two relevant values on a matrix to find what you need to roll.

I feel almost every gamer is mixed up on #1. When you have AD&D using d6 for elves to find secret doors and d4 for dwarfs to detect shifting walls and d100 for thieves to find traps, that isn't three different mechanics. It's all the same thing. Figure a probability, and roll whatever is convenient.

It's not without its drawbacks. Like you've got an elf creeping around 90' ahead of the party, able to surprise monsters 4 in 6, but then it comes across an ettin that is only surprised 1 in 10. Technically, you've got 2 salient variables opposing one another. This should be solved by a matrix. But it might seem silly to have a matrix with indices like 1 in 10 or 4 in 6. So if you don't want to go that route, and you don't want to have a stroke doing the math, you need a common denominator.

Which means going back to the organic pecking order, if the top tier isn't working, the only way to avoid the bottom tier is to go percentile.

It's a good way to go. And most objectives to it are completely idotic.

But still, I do want to use all the goddamn dice I paid for.

Simple answer - they're swingy as shit.

Settings is my guess. Outside CoC what cool setting do they have? None. Sure, Glorantha is neat, but definitely not everyone's cup of Joe. That and there's no really good magic systems.

QuoteSimple answer - they're swingy as shit.

But that really depends on how character abilities are counted and developed.

Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

Quote from: drayakir on July 15, 2022, 09:35:54 PM
Simple answer - they're swingy as shit.

So is the d20, but that hasn't stopped it from being the market leader.

Quote from: Jason Coplen on July 15, 2022, 09:53:37 PM
Settings is my guess. Outside CoC what cool setting do they have? None. Sure, Glorantha is neat, but definitely not everyone's cup of Joe. That and there's no really good magic systems.

D&D's magic system is crap, but it's still the market leader. Granted I'm not very familiar with any d100 based systems and haven't played any of them in decades, so I'm not sure any of them are any better.

D&D has a couple of cool settings at least, but they've never been its main selling point, and they keep changing the default setting every edition. I'm not sure that's why it and its derivatives are the best selling games.

Quote from: drayakir on July 15, 2022, 10:23:04 PM
Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

Do you mean rolling high? I prefer roll under, personally. Both are percentile.

Bell curve ain't bad except for combat, which is a wild affair linear handles better.

Quote from: VisionStorm on July 15, 2022, 10:47:58 PM

Quote from: Jason Coplen on July 15, 2022, 09:53:37 PM
Settings is my guess. Outside CoC what cool setting do they have? None. Sure, Glorantha is neat, but definitely not everyone's cup of Joe. That and there's no really good magic systems.

D&D's magic system is crap, but it's still the market leader. Granted I'm not very familiar with any d100 based systems and haven't played any of them in decades, so I'm not sure any of them are any better.

D&D has a couple of cool settings at least, but they've never been its main selling point, and they keep changing the default setting every edition. I'm not sure that's why it and its derivatives are the best selling games.

Touche. I cannot argue against that. Maybe I'll get back to you after I pull my foot out of my mouth. ;)

Nobody can touch D&D in name recognition. People ask me - what's RuneQuest and my default answer is - it's like D&D, only grittier. Unless some tv show that hits big makes a big todo about some other tabletop rpg D&D has no chance of being dethroned. At least currently. Pale Puppy was huge in the 1990s riding the success of vampire books and movies, including The Crow.

Quote from: drayakir on July 15, 2022, 10:23:04 PM
Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

One thing I like about expressing odds as a percentage is it's a lot easier to highlight the severe analytical defects in what you're saying. Which I think is important because a lot of gamers would agree with you. And it's straight up incorrect.

Take GURPS. There you have the iconic 3d6 bell curve that gets gamers rocks off. It's simple. Uses dice that's familiar even to the normies. They can be added up quickly. And it's high enough resolution that the probability distribution actually looks like a pretty damn sexy bell curve. Nothing but great things to say about it.

How does that work in practice. Well, my guy as 12 Dex and a +3 in Stabbing Sword skill. So I need a 15 or under to hit. That's roughly a 95% (rounding to the nearest integer) chance to hit. Got it. Switch systems.

Now I've got my Lejendary Adventure Avatar with 75 Weapons Ability, and the Stabbing Sword has a Precision bonus of 20. That's roughly a 95% chance to hit. Same thing. Because "swingy" is made up nonsense when your answering a question of "Did you do what you set out to do?" Either you do or you don't. And the probability that you do always boils down to a percentage.

I know what you're saying. But muh modifiers!

So now GURPS man is going for the coveted called shot through the eye socket to the brain, bypassing the natural armor of the skull, for -10 to hit. Now he needs 5 or under. Drops the probability to 5%.

LA guy, not to be outdone, goes for the same shot. Aimed attack means -20 to hit. And then to bypass armor requires getting a special success--rolling under 1/10 the probability. So 95 - 20 = 75, so you have to roll 7 or less. 7%. Not really a huge difference.

And yeah, I know there's someone somewhere thinking "Ackchyually 7 hits in 100 is 40% more hits than 5 in 100." But when there's no frame of reference to say which is more correct we are in fact operating within the margin of noise. It's clearly a similar order of magnitude in the adjustments.


The trick that gets pulled in these sorts of discussions is every argument you can make is hypothetical. As such, it makes assumptions that usually are not applicable to an actual play situation. That's why I cite specific rules from specific systems. It's a waste of time to speak in generalities like this type of mechanic does this, but that other type of mechanic does that.

If you're talking about a situation that's relevant to the game, and if the game was play-tested, I have to think the problem arose at some point, was addressed, and is not an actual problem. Maybe some games weren't as rigorously tested and put together as others. An example of a bad game is just that--an example of a bad game. Not evidence of a bad mechanic.

Quote from: Jason Coplen on July 15, 2022, 09:53:37 PM
Settings is my guess. Outside CoC what cool setting do they have? None. Sure, Glorantha is neat, but definitely not everyone's cup of Joe. That and there's no really good magic systems.

Well, Eclipse Phase has an interesting enough setting, but it's not to everyone's liking.

Quote from: HappyDaze on July 15, 2022, 11:35:31 PM

Quote from: Jason Coplen on July 15, 2022, 09:53:37 PM
Settings is my guess. Outside CoC what cool setting do they have? None. Sure, Glorantha is neat, but definitely not everyone's cup of Joe. That and there's no really good magic systems.

Well, Eclipse Phase has an interesting enough setting, but it's not to everyone's liking.

I've never looked at it. I'm ignorant as Hell when it comes to the game, except I know it's SF.

Percentages are too tangible and a given percentage may not feel right even if accurate. +1 on a d20 feels better that +5% on d100% to most people. 5% chance of failing catastrophically at a mundane time sensitive task is absurd but a 1 on a d20 is accepted.

Quote from: Lunamancer on July 15, 2022, 11:32:03 PM

Quote from: drayakir on July 15, 2022, 10:23:04 PM
Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

One thing I like about expressing odds as a percentage is it's a lot easier to highlight the severe analytical defects in what you're saying. Which I think is important because a lot of gamers would agree with you. And it's straight up incorrect.

Take GURPS. There you have the iconic 3d6 bell curve that gets gamers rocks off. It's simple. Uses dice that's familiar even to the normies. They can be added up quickly. And it's high enough resolution that the probability distribution actually looks like a pretty damn sexy bell curve. Nothing but great things to say about it.

How does that work in practice. Well, my guy as 12 Dex and a +3 in Stabbing Sword skill. So I need a 15 or under to hit. That's roughly a 95% (rounding to the nearest integer) chance to hit. Got it. Switch systems.

Now I've got my Lejendary Adventure Avatar with 75 Weapons Ability, and the Stabbing Sword has a Precision bonus of 20. That's roughly a 95% chance to hit. Same thing. Because "swingy" is made up nonsense when your answering a question of "Did you do what you set out to do?" Either you do or you don't. And the probability that you do always boils down to a percentage.

I know what you're saying. But muh modifiers!

So now GURPS man is going for the coveted called shot through the eye socket to the brain, bypassing the natural armor of the skull, for -10 to hit. Now he needs 5 or under. Drops the probability to 5%.

LA guy, not to be outdone, goes for the same shot. Aimed attack means -20 to hit. And then to bypass armor requires getting a special success--rolling under 1/10 the probability. So 95 - 20 = 75, so you have to roll 7 or less. 7%. Not really a huge difference.

And yeah, I know there's someone somewhere thinking "Ackchyually 7 hits in 100 is 40% more hits than 5 in 100." But when there's no frame of reference to say which is more correct we are in fact operating within the margin of noise. It's clearly a similar order of magnitude in the adjustments.


The trick that gets pulled in these sorts of discussions is every argument you can make is hypothetical. As such, it makes assumptions that usually are not applicable to an actual play situation. That's why I cite specific rules from specific systems. It's a waste of time to speak in generalities like this type of mechanic does this, but that other type of mechanic does that.

If you're talking about a situation that's relevant to the game, and if the game was play-tested, I have to think the problem arose at some point, was addressed, and is not an actual problem. Maybe some games weren't as rigorously tested and put together as others. An example of a bad game is just that--an example of a bad game. Not evidence of a bad mechanic.

Obviously it's all hypothetical. Ultimately it comes down to personal preference. But the thing happens with descriptions. If you're described as a "grandmaster" at a skill, you should never fail at a basic task. I prefer looking at the Shadowrun 4e system that does it much better. An easy task requires just 1 success. A character that is considered to be a grandmaster of something is going to have something to the tune of 14 dice not counting equipment bonuses. The odds of getting at least 1 success on that many dice is 99.66%. Sure you have the statistical fluke of rolling no dice on that many, but the odds are well, less than 1%. Now if we're using CoC as an example, at character generation, someone who represents the utmost master of a skill is... 75%? I think? It's been a while since I've looked at the system. Regardless, it doesn't even reach 90%. So, the Shadowrunner is going to have a good 20% odds of success on the bleeding edge researcher in CoC. It is also important to note that the CoC character has a flat 1% chance of failure. Then if we compare them to the poor D&D adventurer, they're just fucked. They have a flat 5% chance of failing any roll, but barring that, if we're looking at the modern edition, with it's "bounded accuracy" the character is going to have something to the tune of +5 to their primary skill at chargen (3 from stat at 17, 2 from proficiency). An easy task is a DC 10, so the starting character has a 25% chance of failure.

And all this is because the d100 can just randomly decide to fuck you.

Roll under systems are a little off-putting to some slice of the gamer population.  It's not an insurmountable problem with most gamers, but it is there.  Roll over percentile would be an odd duck. Not saying it can't work, but might be a little twisted in interpretation, possibly throwing out some of the intuitive benefits supposedly residing in using the percentile system in the first place.

There's no point in having the fine granularity of percentiles if your system doesn't take advantage of it.  Exactly how it does so can lead to some compromises.  In an attempt to write my "inspired by Dragon Quest" game, I found that using the fine grain of the percentiles to slow advancement was still useful, but for modifiers applied on the fly (e.g. typical combat or spell modifiers), I very much wanted to stick with 10% increments whenever possible, and 5% increments when the 10% was too coarse.  Playing around with +1% or +2% per some factor (e.g. shield rank) in DQ uses the heck out of the fine granularity, but that's also part of what makes it inaccessible.  Since "advancement" happens away from the action, it can afford to take advantage of the finer grain without it bogging everything down.  (Done well, such as in most of the later RQ editions and their variants, such fine grain advancement can also give a moderate sense of verisimilitude without a lot of complication, too.  DQ manages to throw that advantage away by inserting layers and layers of complication on top of an otherwise good system.)

Quote from: jhkim on July 15, 2022, 07:30:50 PM

3) Percentile stats make it difficult to express large differences like in high-power fantasy or superheroes, because values higher than 100% are counter-intuitive.

This is a lot bigger deal than it seems at first.  When just talking about it, seems like it would be something to work around, but when you start designing the game, turns out not so much.  That's because to take advantage of the full percentile range is probably out the door in reality, when mixed with slow, "realistic" advancement of a reasonably simple percentile system.  Be real, not many people are going to want to play a game where you start at 1% and work up slowly from there.  The skills are practically unusable for a long time.  And no system of which I'm aware does so.  They'll start off at some base, usually, in the 20% to 40% range, perhaps based on ability scores, or like DQ just set by fiat based on what the ability is.  Tolerances for what is good enough varies by players, but in my experience most players will tolerate a floor somewhere in the 25% to 50% range, depending on the rate of advancement.  So let's round all that off and say we've tossed out about a third of the percentile range right up front.  You have a similar (if narrower) dynamic on the upper end, that I won't elaborate upon since this post is already long.  So to make a long story short, your usable range is probably more in the 20% to 95% range, with the vast majority of abilities more in the 40% to 85% range.

(A similar dynamic is of course true for any mechanic, where the extremes of the range limit what you can do with it and shape the modifiers.  Once you get down small enough that your useful, typical modifier is +1 or +2 on a relatively narrow spread, say 1d20 or 3d6, no one expects fine grain anymore.  That's the subtle difference.)

Now combine all that.  We are trying to keep most starting points in the 40% to 85% range, allowing for modifiers that are usually in 10% increments, with characters that start on the lower end of that and very slowly work up to the upper end of it.  All doable, if a little flaky when several positive or negative modifiers send things out the 1-100 range.  But let's wave that off and say we can account for such exceptions with a tolerable level of complexity.  The resulting system might be really nice for that slow advancement.  If you start trying to live in the upper or lower ranges, or speed up advancement, all of your advantages and compromises hit the wall really fast.  You might be able to work around that to a certain extent by scaling something other than the percentile roll.  For example, higher powered characters don't advance skill rolls any faster than the usual slow rate, but what they do with success is more impressive.  Note that this is itself a compromise on the design that might seem a little contrived after awhile.

Trying to use percentile, roll under for a D&D style game would be about a useless as trying to make a d20 Star Wars (Ha!).  It's the wrong tool for the job.  Using it makes the most sense when you want incremental advancement and a fairly overt power cap.

Quote from: drayakir on July 16, 2022, 12:22:56 AM
Obviously it's all hypothetical. Ultimately it comes down to personal preference.

There are key variables that can turn the conclusions on their heads that hypotheticals have the luxury of excluding all "for the sake of argument" that are not excluded in reality. Sound analysis identifies those variables. And a sound hypothetical includes them. This isn't a matter of preference. It's a matter of accurate analysis versus obsession with a model.

QuoteBut the thing happens with descriptions. If you're described as a "grandmaster" at a skill, you should never fail at a basic task. I prefer looking at the Shadowrun 4e system that does it much better. An easy task requires just 1 success. A character that is considered to be a grandmaster of something is going to have something to the tune of 14 dice not counting equipment bonuses. The odds of getting at least 1 success on that many dice is 99.66%. Sure you have the statistical fluke of rolling no dice on that many, but the odds are well, less than 1%. Now if we're using CoC as an example, at character generation, someone who represents the utmost master of a skill is... 75%? I think?

I used to work with this 60 year old guy, one day he comes to work holding this big trophy. He won 2nd place national grandmaster body building competition. Sounds impressive, especially for a 60 year old. Until you find out that "grandmaster" was the name they gave to their division for older body builders who were past their prime. Kudos to the guy for competing and winning. The point is, that's a very different level of performance than coming in 2nd place in a tournament of grandmasters in chess.

I mean, I couldn't help but notice you mentioned an easy task requires just 1 success. So what does a hard task require? 3? 4? More? So you mean to tell me you could roll something that in game terms is called "success" and still fail? And yet you dare complain about how two different games might have different conceptions of a term like "grandmaster" that has no inherent or specific meaning?

It would be the easiest thing in the world to shit on everything you love picking on the stupid word choices of game designers.I prefer to take a more honest approach and look at the numbers to make sure I'm comparing apples to apples across systems.

Unless a task has an autofail range (and ones that do are not all that easy), if you have skill over 100 in LA and roll a 100, you roll a second percentile to dice against your points above 100. I don't know what "easy" means in Shadowrun. It could map to anywhere from a +20 to +60 bonus in LA. But whatever the skill plus the "easy" modifier, if it totals out to 166, then you've got a 99.66% chance to succeed. For point of reference, to achieve the highest ranks within an order (guild), the required score in the main skill has to be at least 131. So a 136 +30 easy bonus both fit's LA's idea of "grandmaster" and "easy" and yields the same probability. Apples to apples.

QuoteIt's been a while since I've looked at the system. Regardless, it doesn't even reach 90%. So, the Shadowrunner is going to have a good 20% odds of success on the bleeding edge researcher in CoC. It is also important to note that the CoC character has a flat 1% chance of failure. Then if we compare them to the poor D&D adventurer, they're just fucked. They have a flat 5% chance of failing any roll, but barring that, if we're looking at the modern edition, with it's "bounded accuracy" the character is going to have something to the tune of +5 to their primary skill at chargen (3 from stat at 17, 2 from proficiency). An easy task is a DC 10, so the starting character has a 25% chance of failure.

Two problems. What you're saying is grain-bitching. And what you're saying is also not true.

Every probability distribution approximates an S-curve just by virtue of the fact that probabilities are bounded. Yeah, even if the RPG doesn't have "bounded probability" probability is always bounded by 0 and 1. The question is what happens when you approach the bounds. Yeah, you could just say on a d20, 1 always fails, 20 always succeeds, and the curve goes horizontal at the 5% away from the bounds. A d100 system where 1 always succeeds and 100 always fails would similarly go horizontal, only at the 1% mark instead. But there could also be a tapering-out effect as I described with LA. But in all 3 of these cases, we're talking about a difference of less than 5% entirely attributable to the graininess of the mechanic. Now if I've correctly reversed engineered Shadowrun as you describe it, having only 1 die means 33% chance of succeeding as an easy task. What if you have two dice? You're going to skip straight to 55%? Sorry. You don't get to bitch about a rounding error within 5% while a rounding error in excess of 20% is fine.

And to the second point. It's just plain not true. When I play AD&D 1E, I can hit a magically held or sleeping character without any chance of failure at all. There's no whiff factor for things that are that easy. This isn't something that you will find emerging from the math. But it's how people play, and it is also there officially in the rules. Obsession over the model is going to make you blind to what is plain to see in actual play. You're simultaneously asserting that something that is noticeable and a problem, but also it won't be noticed and handled like a problem at the point of play. That's a thin line to tread.

QuoteAnd all this is because the d100 can just randomly decide to fuck you.

I have an old-school d100 I bought for $3 back in 1989. In all this time, it has never once rolled out of my dice bag under its own volition and then fornicated with anyone.

The d100 is just too big. Is there a meaningful difference between 71% chance of doing something, and a 74%?

I'll also note that I feel like going for d100 lends itself to either: Roll-under systems (feels bad & counterintuitive), or reducing attribute systems (also feels bad & counterintuitive).

What I like about d100 systems is they generally have you modify your target number before rolling, so success or failure is immediately apparent once you roll. d20 systems tend to have you add/subtract modifiers after the roll, so there's a short delay as you do the arithmetic. It's a primitive gambler mental thing that hits the right neurons and has nothing to do with the actual dice involved.

Quote from: Zelen on July 16, 2022, 02:59:11 PM
The d100 is just too big. Is there a meaningful difference between 71% chance of doing something, and a 74%?

I agree about there is no statistical difference between a few percentage points, but the 1s place is useful in tracking incremental skill improvement.

For me the basic problem is that I like probability not being obvious by simply looking directly at the numbers. I find it immersion-breaking to immediately know I have a 50% chance of failure when rolling my Arcane Lore 60 Skill vs. a -10 Difficulty Modifier. (Yes, if you're good enough at math or seasoned enough with the system you get a pretty clear sense of your odds anyway, but there is something a little different about how obvious percentiles make it.)

The double-digit mental addition or subtraction required for modifiers which use increments of other than 5% or 10% (and if you don't use increments other than that, it's simpler to go to the d20, as noted) is also, I think, a stumbling block for enough gamers that it's an immersion-breaker. And there are others who simply don't like roll-under -- I'm one of them; I wouldn't turn down a chance to play such a system if offered (and I spent years playing GURPS), but my preferences are always for the high roll.

None of this makes percentiles a bad or unplayable system. It's just reason enough for me to explain why they haven't driven all other alternatives out of the market.

Quote from: Jason Coplen on July 15, 2022, 11:18:17 PM

Quote from: drayakir on July 15, 2022, 10:23:04 PM
Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

Do you mean rolling high? I prefer roll under, personally. Both are percentile.

Bell curve ain't bad except for combat, which is a wild affair linear handles better.

With d100 % Rolls, I'm Always thinking about Roll Under; as in a 30% Chance of Success means, you need to Roll 30 or Under on d100.

Quote from: Jam The MF on July 16, 2022, 07:05:20 PM

Quote from: Jason Coplen on July 15, 2022, 11:18:17 PM

Quote from: drayakir on July 15, 2022, 10:23:04 PM
Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

Do you mean rolling high? I prefer roll under, personally. Both are percentile.

Bell curve ain't bad except for combat, which is a wild affair linear handles better.

With d100 % Rolls, I'm Always thinking about Roll Under; as in a 30% Chance of Success means, you need to Roll 30 or Under on d100.

I love the simplicity of it. You know your odds before rolling, meaning most players will roll regardless. I much prefer it to any game using "yes, but" rolling. I find it easier to roll, know your result, and move on. Too much dice rolling takes me out of the game.

Quote from: Jason Coplen on July 16, 2022, 08:05:46 PM

Quote from: Jam The MF on July 16, 2022, 07:05:20 PM

Quote from: Jason Coplen on July 15, 2022, 11:18:17 PM

Quote from: drayakir on July 15, 2022, 10:23:04 PM
Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

Do you mean rolling high? I prefer roll under, personally. Both are percentile.

Bell curve ain't bad except for combat, which is a wild affair linear handles better.

With d100 % Rolls, I'm Always thinking about Roll Under; as in a 30% Chance of Success means, you need to Roll 30 or Under on d100.

I love the simplicity of it. You know your odds before rolling, meaning most players will roll regardless. I much prefer it to any game using "yes, but" rolling. I find it easier to roll, know your result, and move on. Too much dice rolling takes me out of the game.

It gets straight to the point.  d100 is finite.  You can adjust in large increments, or in very small increments.  It is flexible for the DM.

A D20 system with +/- increments of 1 is mathematically the same as a percentile system that uses increments of 5%. 

The systems I'm more curious about are all of the games that stick to just the humble D6.  Dice pools or a single 1D6, or classic 2D6 get the most uses.   Or even a D36 system that uses the dice to generate a tens number from 10 to 60, and the other die is the single digit 1 to 6.  A range of 11-66, aka 36 possible numbers. 

All that work just to use common dice.  It's all probably unnecessary now that gaming dice can be bought at Walmart, or dice apps for your phone exist.  Hell, just use a web browser and search "dice roller" if you want. 

Still, I'm a sucker for easy to use dice mechanics.  Dungeons and Delvers Dice Pool Edition for example.  Attribute stats and skill levels are each a dice size, plus any other benefit are also a dice size.  Roll them, pick the best two and add.  Simple.

Quote from: Jam The MF on July 15, 2022, 07:13:11 PM
Having a % Chance of Being Successful at "X", is a very natural way of explaining things.

Why haven't Percentile-Based Systems won out in a big way, in the RPG market?

Thanks in advance, for chiming in.

I mean, technically, every game that uses dice is a % system, its just that d20 uses increments of 5% and is explained without using percent.   I think d100 has its place, its just easier to roll 1d20 than it is to roll 2d10 and turn it into d100,  or to roll an actual d100 and wait for it to stop rolling and then peek on the tiny sides for the correct number

I'll throw in a monkey-wrench...

MSH is a percentile based system that has built in mechanics that can make sure you almost always succeed (Karma). But the entirety of this discussion has been straight pass/fail mechanics based on the actual number... It is one of the most un-swingy games I've ever run. When people fail, it's almost always because they don't want to spend Karma.

How many percentile systems have graduated varying success when rolling percentile against an easy to use chart? With Karma mechanics (or whatever you want to allow to modify that roll on the fly) you can get one very streamlined and fun system.

Quote from: Jason Coplen on July 15, 2022, 11:28:14 PM

Quote from: VisionStorm on July 15, 2022, 10:47:58 PM

Quote from: Jason Coplen on July 15, 2022, 09:53:37 PM
Settings is my guess. Outside CoC what cool setting do they have? None. Sure, Glorantha is neat, but definitely not everyone's cup of Joe. That and there's no really good magic systems.

D&D's magic system is crap, but it's still the market leader. Granted I'm not very familiar with any d100 based systems and haven't played any of them in decades, so I'm not sure any of them are any better.

D&D has a couple of cool settings at least, but they've never been its main selling point, and they keep changing the default setting every edition. I'm not sure that's why it and its derivatives are the best selling games.

Touche. I cannot argue against that. Maybe I'll get back to you after I pull my foot out of my mouth. ;)

Nobody can touch D&D in name recognition. People ask me - what's RuneQuest and my default answer is - it's like D&D, only grittier. Unless some tv show that hits big makes a big todo about some other tabletop rpg D&D has no chance of being dethroned. At least currently. Pale Puppy was huge in the 1990s riding the success of vampire books and movies, including The Crow.

Good luck. This is 90s nostalgia:
(https://ctl.s6img.com/society6/img/JLMl13coU-J2EhYg3cXh4atEmx4/w_1500/prints/~artwork/s6-original-art-uploads/society6/uploads/misc/6f978de4de2b42ccb75ea1da7bb9014f/~~/trapped-in-the-90s-w-iconic-anime-heroine-a-nineties-nostalgia-tribute-prints.jpg)

Quote from: BoxCrayonTales on July 18, 2022, 11:20:59 AM

Quote from: Jason Coplen on July 15, 2022, 11:28:14 PM

Quote from: VisionStorm on July 15, 2022, 10:47:58 PM

Quote from: Jason Coplen on July 15, 2022, 09:53:37 PM
Settings is my guess. Outside CoC what cool setting do they have? None. Sure, Glorantha is neat, but definitely not everyone's cup of Joe. That and there's no really good magic systems.

D&D's magic system is crap, but it's still the market leader. Granted I'm not very familiar with any d100 based systems and haven't played any of them in decades, so I'm not sure any of them are any better.

D&D has a couple of cool settings at least, but they've never been its main selling point, and they keep changing the default setting every edition. I'm not sure that's why it and its derivatives are the best selling games.

Touche. I cannot argue against that. Maybe I'll get back to you after I pull my foot out of my mouth. ;)

Nobody can touch D&D in name recognition. People ask me - what's RuneQuest and my default answer is - it's like D&D, only grittier. Unless some tv show that hits big makes a big todo about some other tabletop rpg D&D has no chance of being dethroned. At least currently. Pale Puppy was huge in the 1990s riding the success of vampire books and movies, including The Crow.

Good luck. This is 90s nostalgia:
(https://ctl.s6img.com/society6/img/JLMl13coU-J2EhYg3cXh4atEmx4/w_1500/prints/~artwork/s6-original-art-uploads/society6/uploads/misc/6f978de4de2b42ccb75ea1da7bb9014f/~~/trapped-in-the-90s-w-iconic-anime-heroine-a-nineties-nostalgia-tribute-prints.jpg)

Blech! You've ruined my day, you bastard! ;)

I don't remember much of the 90s to be honest. I was chained in a basement running rpgs or sitting online in some long dead chat room.

Quote from: Lunamancer on July 16, 2022, 02:20:29 PM

Quote from: drayakir on July 16, 2022, 12:22:56 AM
Obviously it's all hypothetical. Ultimately it comes down to personal preference.

There are key variables that can turn the conclusions on their heads that hypotheticals have the luxury of excluding all "for the sake of argument" that are not excluded in reality. Sound analysis identifies those variables. And a sound hypothetical includes them. This isn't a matter of preference. It's a matter of accurate analysis versus obsession with a model.

QuoteBut the thing happens with descriptions. If you're described as a "grandmaster" at a skill, you should never fail at a basic task. I prefer looking at the Shadowrun 4e system that does it much better. An easy task requires just 1 success. A character that is considered to be a grandmaster of something is going to have something to the tune of 14 dice not counting equipment bonuses. The odds of getting at least 1 success on that many dice is 99.66%. Sure you have the statistical fluke of rolling no dice on that many, but the odds are well, less than 1%. Now if we're using CoC as an example, at character generation, someone who represents the utmost master of a skill is... 75%? I think?

I used to work with this 60 year old guy, one day he comes to work holding this big trophy. He won 2nd place national grandmaster body building competition. Sounds impressive, especially for a 60 year old. Until you find out that "grandmaster" was the name they gave to their division for older body builders who were past their prime. Kudos to the guy for competing and winning. The point is, that's a very different level of performance than coming in 2nd place in a tournament of grandmasters in chess.

I mean, I couldn't help but notice you mentioned an easy task requires just 1 success. So what does a hard task require? 3? 4? More? So you mean to tell me you could roll something that in game terms is called "success" and still fail? And yet you dare complain about how two different games might have different conceptions of a term like "grandmaster" that has no inherent or specific meaning?

It would be the easiest thing in the world to shit on everything you love picking on the stupid word choices of game designers.I prefer to take a more honest approach and look at the numbers to make sure I'm comparing apples to apples across systems.

Unless a task has an autofail range (and ones that do are not all that easy), if you have skill over 100 in LA and roll a 100, you roll a second percentile to dice against your points above 100. I don't know what "easy" means in Shadowrun. It could map to anywhere from a +20 to +60 bonus in LA. But whatever the skill plus the "easy" modifier, if it totals out to 166, then you've got a 99.66% chance to succeed. For point of reference, to achieve the highest ranks within an order (guild), the required score in the main skill has to be at least 131. So a 136 +30 easy bonus both fit's LA's idea of "grandmaster" and "easy" and yields the same probability. Apples to apples.

QuoteIt's been a while since I've looked at the system. Regardless, it doesn't even reach 90%. So, the Shadowrunner is going to have a good 20% odds of success on the bleeding edge researcher in CoC. It is also important to note that the CoC character has a flat 1% chance of failure. Then if we compare them to the poor D&D adventurer, they're just fucked. They have a flat 5% chance of failing any roll, but barring that, if we're looking at the modern edition, with it's "bounded accuracy" the character is going to have something to the tune of +5 to their primary skill at chargen (3 from stat at 17, 2 from proficiency). An easy task is a DC 10, so the starting character has a 25% chance of failure.

Two problems. What you're saying is grain-bitching. And what you're saying is also not true.

Every probability distribution approximates an S-curve just by virtue of the fact that probabilities are bounded. Yeah, even if the RPG doesn't have "bounded probability" probability is always bounded by 0 and 1. The question is what happens when you approach the bounds. Yeah, you could just say on a d20, 1 always fails, 20 always succeeds, and the curve goes horizontal at the 5% away from the bounds. A d100 system where 1 always succeeds and 100 always fails would similarly go horizontal, only at the 1% mark instead. But there could also be a tapering-out effect as I described with LA. But in all 3 of these cases, we're talking about a difference of less than 5% entirely attributable to the graininess of the mechanic. Now if I've correctly reversed engineered Shadowrun as you describe it, having only 1 die means 33% chance of succeeding as an easy task. What if you have two dice? You're going to skip straight to 55%? Sorry. You don't get to bitch about a rounding error within 5% while a rounding error in excess of 20% is fine.

And to the second point. It's just plain not true. When I play AD&D 1E, I can hit a magically held or sleeping character without any chance of failure at all. There's no whiff factor for things that are that easy. This isn't something that you will find emerging from the math. But it's how people play, and it is also there officially in the rules. Obsession over the model is going to make you blind to what is plain to see in actual play. You're simultaneously asserting that something that is noticeable and a problem, but also it won't be noticed and handled like a problem at the point of play. That's a thin line to tread.

QuoteAnd all this is because the d100 can just randomly decide to fuck you.

I have an old-school d100 I bought for $3 back in 1989. In all this time, it has never once rolled out of my dice bag under its own volition and then fornicated with anyone.

Well, your counterpoint has several flaws. First off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number. So no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

If you're complaining about nomenclature, then we'll just say that "grandmaster" refers to the top tier in skill mastery. If you're a grandmaster, this means that you're like, in the top 20 people in the planet in that skill.

And as far as Shadowrun goes, the scale is given as such: 1 is easy, 2 is average, 4 is hard, 6 is extreme. It is possible to have a target number above 6, but that's when there's an opposed check involved and someone rolled higher than 6. Then you need to match of exceed that. So, 6 successes means you can succeed at the most difficult task within the system. Which means that our human grandmaster has the following odds of success:

The probability of 6 successes or more is 31.0192476681325
The probability of 5 successes or more is 52.4499531567108
The probability of 4 successes or more is 73.8806586452891
The probability of 3 successes or more is 89.4666262733461
The probability of 2 successes or more is 97.2596100873746
The probability of 1 success or more is 99.6574512609218
The probability of no successes is 0.34254873907823
(http://www.unseelie.org/cgi-bin/shadow.cgi?number=14&target=5&cumulus=1&action=Press+once+to+send (http://www.unseelie.org/cgi-bin/shadow.cgi?number=14&target=5&cumulus=1&action=Press+once+to+send))

This makes much more sense than a flat failure/success rate of a single dice system.

Furthermore, you keep saying that 1% or 5% is just graininess. That's a great way to dismiss it, but it doesn't make sense. You said yourself that really our two numbers are 0 and 1, which I agree with. So with a dice pool system, I know that I'm going to succeed X%, but the d20 has a fuzziness rating of 10% (from the 1 and 20 face) and the d100 has a fuzziness rating of 2% (the 1 and 100 faces). Would it not be better to have something with no fuzziness?

The answer is yes. There are only disadvantages to using a single die over a dice pool.

Quote from: Jam The MF on July 15, 2022, 07:13:11 PMWhy haven't Percentile-Based Systems won out in a big way, in the RPG market?

I would argue that they have won out in a big way in as much as any non-D&D system has. CoC and Runequest are among the few long-standing games in this industry.

Quote from: drayakir on July 18, 2022, 12:45:14 PM
Well, your counterpoint has several flaws. First off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number. So no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

The answer is yes. There are only disadvantages to using a single die over a dice pool.

Who is going to make a player roll just to mount a horse? Are you purposely this dense?

Quote from: drayakir on July 18, 2022, 12:45:14 PM
There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

Do you really roll for that kind of stuff though? I don't call for rolls unless there so some risk of failure and that the failure would have a meaningful consequence (injury, wasting limited time, etc.). Mounting a horse in ideal conditions does not require a roll from a grandmaster nor any other adventure for that matter.

5% is a pretty decent crit/fumble rate when circumstances provide for risk. Also, some d100 systems use a crit/fumble range that changes size depending on your skill. In those systems, a grandmaster would have a 1% chance of fumbling mounting a horse in situations where that action is risky, like the horse is moving, the grandmaster's jumping off a roof, etc.

Long ago I had a thief fumble their backstab roll. One a prone target, who was already wounded. It was stupid. Today I would declare that an automatic hit with no roll.

Reading the 4e BRP rulebook, the percentile system does have multiple difficulty levels and multiple degrees of success. Dice pool systems have no advantage in this regard.

Quote from: Jason Coplen on July 18, 2022, 01:59:37 PM

Quote from: drayakir on July 18, 2022, 12:45:14 PM
Well, your counterpoint has several flaws. First off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number. So no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

The answer is yes. There are only disadvantages to using a single die over a dice pool.

Who is going to make a player roll just to mount a horse? Are you purposely this dense?

It's what si known as an example. I could've come up with any sort of basic skill that a grandmaster would have. For instance, spelling their own name when rolling a Writing check. A d100/d20 system would say that on a nat 1, you fuck that up, somehow. A 5% or 1% chance. Whereas with a dice pool system, the odds aren't 0, but they're sufficiently close where the difference doesn't matter.

It's pointless to argue about the arbitrariness of a 1%/5% chance of failure for some routine task, because good GMs shouldn't be asking for rolls like that. Most games put in print that the expectation is that rolls are for situations where consequences have narrative significance.

Even if you did ask for rolls like that, a good GM has the power to define the scope of the failure, or ask for another roll, or just ignore the failure.

Quote from: drayakir on July 18, 2022, 07:08:24 PM

Quote from: Jason Coplen on July 18, 2022, 01:59:37 PM

Quote from: drayakir on July 18, 2022, 12:45:14 PM
Well, your counterpoint has several flaws. First off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number. So no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

The answer is yes. There are only disadvantages to using a single die over a dice pool.

Who is going to make a player roll just to mount a horse? Are you purposely this dense?

It's what si known as an example. I could've come up with any sort of basic skill that a grandmaster would have. For instance, spelling their own name when rolling a Writing check. A d100/d20 system would say that on a nat 1, you fuck that up, somehow. A 5% or 1% chance. Whereas with a dice pool system, the odds aren't 0, but they're sufficiently close where the difference doesn't matter.

Dude, I don't even entirely disagree with the original point you were trying to make (I don't really care very much and think it's pointless nitpicking, but I wouldn't say you're wrong on principle per se), but this example is BAD, and it isn't even true for ANY system, cuz no system makes you roll for routine pointless tasks. If anything they do the complete opposite and explicitly tell you not to roll unless it matters.

And climbing on top of a horse under completely normal circumstances (when the horse isn't even moving and you're not in the middle of combat) or trying to write your name doesn't matter. And in circumstances where it does matter (you're trying to jump onto a moving mount in the middle of combat), having a 1% or even a 5% chance of automatic failure isn't such a big deal. Things have a way of going south when you're working under pressure IRL all the time.

Quote from: drayakir on July 18, 2022, 07:08:24 PM

Quote from: Jason Coplen on July 18, 2022, 01:59:37 PM

Quote from: drayakir on July 18, 2022, 12:45:14 PM
Well, your counterpoint has several flaws. First off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number. So no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

The answer is yes. There are only disadvantages to using a single die over a dice pool.

Who is going to make a player roll just to mount a horse? Are you purposely this dense?

It's what si known as an example. I could've come up with any sort of basic skill that a grandmaster would have. For instance, spelling their own name when rolling a Writing check. A d100/d20 system would say that on a nat 1, you fuck that up, somehow. A 5% or 1% chance. Whereas with a dice pool system, the odds aren't 0, but they're sufficiently close where the difference doesn't matter.

Fair enough. It seems you're talking basic odds with no DM intervention of sorts. Am I correct in thinking this?

Quote from: Jason Coplen on July 18, 2022, 01:59:37 PM

Quote from: drayakir on July 18, 2022, 12:45:14 PM
Well, your counterpoint has several flaws. First off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number. So no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

The answer is yes. There are only disadvantages to using a single die over a dice pool.

Who is going to make a player roll just to mount a horse? Are you purposely this dense?

Maybe if the PC is playing a city boy, who's never been on a horse before.  It is possible for such a person to fall and bust their tail.

Quote from: Jason Coplen on July 18, 2022, 08:42:30 PM

Quote from: drayakir on July 18, 2022, 07:08:24 PM

Quote from: Jason Coplen on July 18, 2022, 01:59:37 PM

Quote from: drayakir on July 18, 2022, 12:45:14 PM
Well, your counterpoint has several flaws. First off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number. So no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

The answer is yes. There are only disadvantages to using a single die over a dice pool.

Who is going to make a player roll just to mount a horse? Are you purposely this dense?

It's what si known as an example. I could've come up with any sort of basic skill that a grandmaster would have. For instance, spelling their own name when rolling a Writing check. A d100/d20 system would say that on a nat 1, you fuck that up, somehow. A 5% or 1% chance. Whereas with a dice pool system, the odds aren't 0, but they're sufficiently close where the difference doesn't matter.

Fair enough. It seems you're talking basic odds with no DM intervention of sorts. Am I correct in thinking this?

Correct. I am talking probability trends in the resolution mechanic system. I obviously agree that a good GM is going to say "Okay, the person who was literally raised on horse milk, blessed by the Horse Goddess Epona, has been in the saddle since she was three, has tamed hundreds of stallions? She doesn't need to make a roll to mount a horse."

Quote from: drayakir on July 19, 2022, 01:02:43 PM
Correct. I am talking probability trends in the resolution mechanic system. I obviously agree that a good GM is going to say "Okay, the person who was literally raised on horse milk, blessed by the Horse Goddess Epona, has been in the saddle since she was three, has tamed hundreds of stallions? She doesn't need to make a roll to mount a horse."

I think if you present a realistic example, you will find that a 1% or 5% chance of a blunder is reasonable. Also, as Zelen said the scope of the blunder is up to the GM. Suppose it is raining and muddy, so the grandmaster must roll to mount the horse. Oops, it's a 1. So he slips and muddies himself. No big deal. A complete novice rider, on the other hand, might break his arm.

Statistical differences in two reasonably designed systems don't matter in play. Other factors, such as GM discretion and die quality, overshadow statistical differences. Besides, comparing raw percentages is one thing, but a chi-squared or similar measure of significance is another. How many rolls would need to be made, with real dice on a real table, before the difference between two systems is statistically significant? Give me a dice pool setup that models a typical PC in a d20 system, and I will run that test myself.

Quote from: drayakir on July 19, 2022, 01:02:43 PM
Correct. I am talking probability trends in the resolution mechanic system. I obviously agree that a good GM is going to say "Okay, the person who was literally raised on horse milk, blessed by the Horse Goddess Epona, has been in the saddle since she was three, has tamed hundreds of stallions? She doesn't need to make a roll to mount a horse."

What matters for how "swingy" a system rates is a comparison of:

(1) The attribute scale of the system
(2) The variance of the die roll used

I commented on this recently in the thread on low-crunch superhero systems (https://www.therpgsite.com/pen-paper-roleplaying-games-rpgs-discussion/low-crunch-superhero-systems/msg1222494/#msg1222494). Olivier Legrand's Crusaders system uses percentile dice, while Steve Kenson's ICONS uses a bell curve 1d6-1d6. However, I think attribute matters more in the Crusaders system. As I put it,

QuoteIn Crusaders, average human is 10, while max attribute can go up to 24. In ICONS, average attribute is 3 while max human is 6 and max superhuman is 10. Even though the die roll is smaller in ICONS, those numbers are very close together. An average human has a fair shot (8%) of beating max human, which is well beyond impossible in Crusaders (average human has only a 5% vs a 19, and 0% against 20 or higher).

If die rolls are over the same range, then a bell curve has lower variance than a linear roll. So, for example, 2d6 has a lower variance than 1d12. However, there are other number ranges at play in a system.

I think C.J. Carella's Cinematic Unisystem and Greg Porter's CORPS are two of the least swingy dice systems, and they both use linear dice (1d10).

Quote from: BoxCrayonTales on July 18, 2022, 04:16:45 PM
Reading the 4e BRP rulebook, the percentile system does have multiple difficulty levels and multiple degrees of success. Dice pool systems have no advantage in this regard.

I don't think BRP went far enough in this area. Instead of just having a skill value and a single special success, they could have had a range of success value.

For example, if a skill value is 110, then it would be written on the character sheet as 110/55/27/13 and a skill value of 45 would be 45/22/11/5

So if you roll the first number or less, it is one success, roll the second number or less for two successes, etc. Now a difficult roll might require a level 2 success to succeed (which is similar to how BRP does it) and if you had a Task, such as picking a lock, that required 3 total successes, you could complete the task with three rolls of 1 success, or one roll of 3 successes.

A contest between two characters would just compare level of success versus each other, so 2 successes would beat 1 success, for instance.

This not only gives value to skills above 100 but it allows more skilled characters to complete tasks not only more often but faster than less skilled characters, again giving value to skills above 100.

That's the way I'd do it.

Quote from: hedgehobbit on July 19, 2022, 04:02:09 PM

Quote from: BoxCrayonTales on July 18, 2022, 04:16:45 PM
Reading the 4e BRP rulebook, the percentile system does have multiple difficulty levels and multiple degrees of success. Dice pool systems have no advantage in this regard.

I don't think BRP went far enough in this area. Instead of just having a skill value and a single special success, they could have had a range of success value.

For example, if a skill value is 110, then it would be written on the character sheet as 110/55/27/13 and a skill value of 45 would be 45/22/11/5

So if you roll the first number or less, it is one success, roll the second number or less for two successes, etc. Now a difficult roll might require a level 2 success to succeed (which is similar to how BRP does it) and if you had a Task, such as picking a lock, that required 3 total successes, you could complete the task with three rolls of 1 success, or one roll of 3 successes.

A contest between two characters would just compare level of success versus each other, so 2 successes would beat 1 success, for instance.

This not only gives value to skills above 100 but it allows more skilled characters to complete tasks not only more often but faster than less skilled characters, again giving value to skills above 100.

That's the way I'd do it.

They have three levels of success: Success, Special and Critical. The SRD omits Critical. You don't need to achieve a particular level of success to achieve an action. Special and Critical just add additional benefits to your success.

Difficulty is applied by modifying the target %. Such as by halving it to represent difficult actions.

Results are already compared in opposed rolls.

How familiar are you with BRP? It already addresses the stuff you're bringing up. Or at least the 4e rulebook does. The SRD is crap.

Quote from: hedgehobbit on July 19, 2022, 04:02:09 PM

Quote from: BoxCrayonTales on July 18, 2022, 04:16:45 PM
Reading the 4e BRP rulebook, the percentile system does have multiple difficulty levels and multiple degrees of success. Dice pool systems have no advantage in this regard.

I don't think BRP went far enough in this area. Instead of just having a skill value and a single special success, they could have had a range of success value.

For example, if a skill value is 110, then it would be written on the character sheet as 110/55/27/13 and a skill value of 45 would be 45/22/11/5

So if you roll the first number or less, it is one success, roll the second number or less for two successes, etc.

hedgehobbit, are you familiar with the James Bond 007 RPG? That is percentile and has four levels of success very similar to what you suggest here. It has a varying multiplier for difficulty, though, which varies with the task.

Quote from: BoxCrayonTales on July 19, 2022, 04:11:30 PMHow familiar are you with BRP? It already addresses the stuff you're bringing up. Or at least the 4e rulebook does. The SRD is crap.

I'm fairly familiar with older versions. Stormbringer was the 2nd campaign I ever ran and my Runequest game was my longest campaign before D&D 3e came out. I understand the BRP already does similar things to what I was talking about, but I find that converting success values into numbered successes, rather than named values, is much more flexible (as you can see in the James Bond 007 RPG). So instead of having a Attack and Defense Matrix like on page 193 of BRP 4e, you just subtract the target's successes from the attacker's. Plus, by having successes listed in numerical values, you can have a list of things to spend those successes on in resolution. For example, 1 success would do damage, but with 2 successes, you could do damage twice, or change the hit location and do damage, or trade both in for a Disarm effect, etc. I prefer systems where you spend successful rolls over system where you have to declare your special action (Called Shots, Disarm, etc) in advance as declaring in advance slows the game down.

For me it is all about speed of resolution and flexibility.

Quote from: jhkim on July 19, 2022, 04:37:10 PMhedgehobbit, are you familiar with the James Bond 007 RPG? That is percentile and has four levels of success very similar to what you suggest here. It has a varying multiplier for difficulty, though, which varies with the task.

Yes, as I mentioned in my previous post, this game is was what changed my mind on using multiples instead of +/- bonuses. The James Bond game was great but the fact that you have two different table lookups per roll was a bit much for me. It also bugged me that a Q4 success was worse than a Q1. They should have swapped those around.

Quote from: Stephen Tannhauser on July 16, 2022, 06:28:46 PM
The double-digit mental addition or subtraction required for modifiers which use increments of other than 5% or 10% (and if you don't use increments other than that, it's simpler to go to the d20, as noted)

Single-digit modifiers can be other than multiples of 5% and also not require double-digit addition or subtraction.

Quote from: Zelen on July 16, 2022, 02:59:11 PM
The d100 is just too big. Is there a meaningful difference between 71% chance of doing something, and a 74%?

There are two major ways I see single-digit modifiers used in percentile RPGs.

1) Cross-feeding. When a character has multiple skills that are applicable to a task, you use the highest and add 10% of the others. It is meaningful to players to know those additional skills count for something, so it does have meaning regardless of how insignificant it may seem to a given set of probabilities.

2) Sometimes the chance being adjusted is highly improbable to begin with. Most commonly, we're talking about "crits," when the percentile roll is under 1/10 the target number. When a small modifier adjusts the die roll rather than the target number, it has disproportionate sway on criticals. That could mean doubling or tripling the odds of a crit. It might also mean halving the odds, or even eliminating the possibility of a crit entirely. And it's hard to argue that's not meaningful.

Quote from: drayakir on July 18, 2022, 12:45:14 PM
Well, your counterpoint has several flaws.

I had points, plural. And "something you disagree with" is not what the word "flaw" means.

QuoteFirst off, you're just outright dismissing the fact that the d20 and d100 system in their most popular incarnations have an auto-pass and auto-fail number.

I wasn't dismissing anything at all. I was focusing on the games I know and play. And every feature I have brought up about d100 games that defeat your arguments appear in at least two different d100 RPGs that have been around for decades and were high profile at one time or another. You don't get to just ignore them. If your assertions are only true for certain RPGs, then it is only those RPGs that have the issues you're mentioning. Not d20 systems in general. Not d100 systems in general.

I mean you do realize CoC is a highly stylized game, right? Some would even say it's supposed to be biased towards making players lose. That makes it not a very good choice as a representative of all d100 games when the issue at hand is the rate of failure inherent in the d100 mechanic.

It's easy to name the most popular d20 system. 5E, of course. But again, we have a problem holding this up as representative of the d20 mechanic. The game was specifically designed with "bounded probability" in mind. It makes no sense to use that as an example when what we're discussing are the extreme ends of the probability distribution.

QuoteSo no matter how good you are, you have a 1% or 5% chance of just failing, regardless of how good you are. That's asinine. There's no reason that someone who is a grandmaster at riding horses is going to fail mounting a horse in ideal conditions. Just not going to happen. But the d100 and d20 system say that yes, you can have the most ideal conditions imaginable, but every 100 times you will fail every 100 times or every 20 times, depending on which system we're using.

Maybe you were referring to *the* d20 system? As in 3E/Pathfinder. That was the game that had Take 10, right? Where you can take the possibility of failure off the table entirely.

Or maybe you were referencing AD&D, where the riding proficiency specifically states you don't need to roll for mounting and dismounting. Success is automatic.

Was there another game that was the most popular incarnation of the d20 system that I missed that has grindmasher skill characters doing pratfalls?

QuoteAnd as far as Shadowrun goes, the scale is given as such: 1 is easy, 2 is average, 4 is hard, 6 is extreme. It is possible to have a target number above 6, but that's when there's an opposed check involved and someone rolled higher than 6. Then you need to match of exceed that. So, 6 successes means you can succeed at the most difficult task within the system. Which means that our human grandmaster has the following odds of success:

The probability of 6 successes or more is 31.0192476681325
The probability of 5 successes or more is 52.4499531567108
The probability of 4 successes or more is 73.8806586452891
The probability of 3 successes or more is 89.4666262733461
The probability of 2 successes or more is 97.2596100873746
The probability of 1 success or more is 99.6574512609218
The probability of no successes is 0.34254873907823

So let's see. Take the reciprocol, and it appears the grand poobah of riding in Shadowrun will be failing 1 in 292 times. Just FYI, if you tossed out the bounded probability in 5E, the best character under ideal circumstances would not only fail only on a 1, but would also have advantage. Meaning he'd have to roll a pair of 1's on 2d20. That's 1 in 400. Suddenly shadowrun guy is starting to look like a comedy relief sidekick.

QuoteThis makes much more sense than a flat failure/success rate of a single dice system.

How? And what is a flat failure? Near as I can tell, the numbers you produced only prove that at the end of the day it all comes down to a percentage. Meaning you can dice it by rolling a d100 with as many extra d10's as you want to have decimal places. No matter how many places you add, no matter how hi-res you want to go, it's still a linear distribution.

QuoteFurthermore, you keep saying that 1% or 5% is just graininess.

Do I keep saying that? Or did I point that out once?

QuoteThat's a great way to dismiss it, but it doesn't make sense. You said yourself that really our two numbers are 0 and 1, which I agree with. So with a dice pool system, I know that I'm going to succeed X%, but the d20 has a fuzziness rating of 10% (from the 1 and 20 face) and the d100 has a fuzziness rating of 2% (the 1 and 100 faces). Would it not be better to have something with no fuzziness?

What's fuzzy?

Every RPG I've ever played or run has things in it that are 0 and 1 probability. Often they're things you just don't roll for. But I have no problem with a mechanic that allows skill and circumstance to add up to high enough (or low enough) that the chance of success is 100% or 0%. Which you do find in AD&D 1E by the way. The six repeating 20's meant some ACs could be impossible to hit. There could be auto-success on item saves. Or is that not a popular enough d20 system to talk about?

QuoteThe answer is yes. There are only disadvantages to using a single die over a dice pool.

I think you were successful in your analysis but you needed 3 successes to be right.

I honestly think it's because writers think they're being clever by using dice in non-traditional ways than just rolling and adding them up. 

I've seen games that use D6's, and count up "successes" that are 4, 5, and 6.   It could be replicated by tossing coins and count how many came up heads. 

Hell, I toyed with making a rules lite game using just a 1D10.  Why?  Because a +1 on a D20, aka 5%, isn't enough of a bonus to me to "feel" significant.  Also, you could play the game using a deck of cards with the face cards and jokers taken out.  It's not logical to play that way, but it does make it a bit interesting to some people like me.  Or because it's different.  No more than that.  It's just different. 

Quote from: Jam The MF on July 15, 2022, 07:13:11 PM
Having a % Chance of Being Successful at "X", is a very natural way of explaining things.

Why haven't Percentile-Based Systems won out in a big way, in the RPG market?

Thanks in advance, for chiming in.

A percentage system does have the advantage of being clear about the chance of success vs failure but sometimes the degree of success or failure is important. In other situations an opposed roll is necessary. On other occasions there isn't one stat or characteristic or skill that is appropriate to test against but a combination. Percentile systems have methods and tools to incorporate these things but it does leave things open for alternative rules.

Similarly the theme of the game may lend itself to a different system.

In truth I am a pretty big fan of percentile systems. 

Quote from: drayakir on July 15, 2022, 10:23:04 PM
Well, I mean I suppose you could have a percentile system that doesn't use a d100, but... I dunno. The problem with the d100 and the d20 that at a certain point your skill/stat doesn't matter. If the target number is 13, and you're at +6, you have very good odds of it, but there's still a decently high chance that you will fail. More, you still run the risk of failing really easy tasks that somebody at your skill level has no business failing. That's why I prefer bell curve stuff, since that distribution is more like a realistic skill distribution.

It's not "swingy" if you can think in terms of probability. If you want less swingy games, start with higher probabilities. Like most things in % games this is remarkably simple. The problem occurs when someone thinks rolling an 18 on 3D6 is toughly the same as rolling a 20 on a d20.

A skill of 19 out of 20, or 95%, or 15 or below on 3D6 means roughly the same: you have about 5% chance of failure. Any bell curve could be calculated as a percentage too. The difference being that a +1 bonus will count differently based on where you are in the 3D6 curve. If you need to roll an 18 on 3D6 a +1 gives roughly +1.4%. If you need an 11 on 3D6 a +1 increases the chance by 12.5%. If you need to roll 100 on % dice a + 5% increased the chance exactly that much.

The real difference is that 3D6 is a bit more confusing to calculate, but to some people it's more fun.

Quote from: Lunamancer on July 19, 2022, 06:35:04 PM
reciprocol,

Reciprocal.

Also, take 10s are an optional rule. And yes, the systems you're shilling for have a flat failure percent.

Quote from: weirdguy564 on July 20, 2022, 08:59:20 AM
I honestly think it's because writers think they're being clever by using dice in non-traditional ways than just rolling and adding them up. 

I've seen games that use D6's, and count up "successes" that are 4, 5, and 6.   It could be replicated by tossing coins and count how many came up heads. 

Hell, I toyed with making a rules lite game using just a 1D10.  Why?  Because a +1 on a D20, aka 5%, isn't enough of a bonus to me to "feel" significant.  Also, you could play the game using a deck of cards with the face cards and jokers taken out.  It's not logical to play that way, but it does make it a bit interesting to some people like me.  Or because it's different.  No more than that.  It's just different.

Both of these die mechanics have been around and used in multiple games (some of them fairly popular, like Shadowrun and Cyberpunk) since at least the 90s or late 80s. Neither is new or different. Some people just like it better than rolling % or d20s.

Quote from: drayakir on July 20, 2022, 11:13:19 AM
Also, take 10s are an optional rule.

LOL. Anything to avoid admitting you straight up have no clue what you're talking about.

QuoteAnd yes, the systems you're shilling for have a flat failure percent.

I haven't shilled for any system; and you still haven't explained what "flat failure" even means.

Quote from: drayakir on July 20, 2022, 11:13:19 AM

Quote from: Lunamancer on July 19, 2022, 06:35:04 PM
reciprocol,

Reciprocal.

Also, take 10s are an optional rule. And yes, the systems you're shilling for have a flat failure percent.

You do realize that in 5E only attack rolls have the 1 and 20 autofail/autosucceed, right? 
For ability checks (skill checks or raw attribute checks) and saving throws you just roll and add and what you get is what you get.

Quote from: Lunamancer on July 20, 2022, 11:56:27 AM

Quote from: drayakir on July 20, 2022, 11:13:19 AM
Also, take 10s are an optional rule.

LOL. Anything to avoid admitting you straight up have no clue what you're talking about.

QuoteAnd yes, the systems you're shilling for have a flat failure percent.

I haven't shilled for any system; and you still haven't explained what "flat failure" even means.

A "flat failure" is when you automatically fail when the dice displays a certain number.

Quote from: moonsweeper on July 20, 2022, 12:02:22 PM

Quote from: drayakir on July 20, 2022, 11:13:19 AM

Quote from: Lunamancer on July 19, 2022, 06:35:04 PM
reciprocol,

Reciprocal.

Also, take 10s are an optional rule. And yes, the systems you're shilling for have a flat failure percent.

You do realize that in 5E only attack rolls have the 1 and 20 autofail/autosucceed, right? 
For ability checks (skill checks or raw attribute checks) and saving throws you just roll and add and what you get is what you get.

Immaterial. An attack is still a dice roll.

Quote from: Trond on July 20, 2022, 09:55:13 AMThe real difference is that 3D6 is a bit more confusing to calculate, but to some people it's more fun.

I found this to be a double edge sword. On one hand, if the probabilities are clear, some players will base their character's action on the probability of success instead of any other story-based reasons, OTOH, if the probabilities are not clear, other players will do incredibly stupid (i.e. suboptimal) things because they don't realize how low their chance of success will end up being.


However, the biggest downside to having to roll multiple dice for each action is what happens if you have to roll for 15 goblins. A single die is much faster in this case. So much so that some games discourage the use of large mobs just to have the game function. IMO, this is too limiting as far as adventure design goes. Even percentage dice can be bulk rolled as you only need to roll the ones dice if the tens dice is in question. For example, if your chance of success is 55 then you only need to roll the ones dice if the tens dice is a 5.

Quote from: drayakir on July 20, 2022, 01:20:49 PM

Quote from: Lunamancer on July 20, 2022, 11:56:27 AM

Quote from: drayakir on July 20, 2022, 11:13:19 AM
Also, take 10s are an optional rule.

LOL. Anything to avoid admitting you straight up have no clue what you're talking about.

QuoteAnd yes, the systems you're shilling for have a flat failure percent.

I haven't shilled for any system; and you still haven't explained what "flat failure" even means.

A "flat failure" is when you automatically fail when the dice displays a certain number.

Quote from: moonsweeper on July 20, 2022, 12:02:22 PM

Quote from: drayakir on July 20, 2022, 11:13:19 AM

Quote from: Lunamancer on July 19, 2022, 06:35:04 PM
reciprocol,

Reciprocal.

Also, take 10s are an optional rule. And yes, the systems you're shilling for have a flat failure percent.

You do realize that in 5E only attack rolls have the 1 and 20 autofail/autosucceed, right? 
For ability checks (skill checks or raw attribute checks) and saving throws you just roll and add and what you get is what you get.

Immaterial. An attack is still a dice roll.

Actually, it is completely 'material' since the items in discussion (ride check to mount a horse and 'taking 10') are specifically skill checks and you brought up 'ideal conditions'.  Attack rolls obviously will have some chance of failure because the PC is under some form of 'stress' during a fight since conditions are never 'ideal' in combat.

Throughout this thread a number of people have indicated that they tend to think in probabilities.  In the case that you KNOW a probability that can be easy to do.  On the other hand, frequently in the game you're asked to create a situation in which you don't know what the probability ought to be. 

Is throwing a grappling hook against a 40' tower significantly different than throwing it against a 20' tower?  If I have an 85% in grapple hooking, does that mean it applies equally to both situations?  Or is one of them 'normal' and I get a +20%/-20% in the other?  What does it mean if I have an 85% in a skill, but I'm also using the skill at -30% or -40%? 

Most people have trouble thinking in probabilities, and comparing relative abilities of different people meaningfully is hard (as has been described above).  If I think that Bruiser the Door Buster has a 95% chance of breaking a door, and Poindexter is half as strong, do I think he should have a 45% chance, or 0%. Is there any skill involved or is it all attribute based?  What if Poindexter is trying to hold the door closed? 

Assigning a fixed TN without considering any of the individuals and then letting them apply their relevant abilities tends to be easier for most people.  If I say that breaking down a door is a TN 20, and someone holding the door is usually a -4, but someone weak and frail only counts as a -2, a lot of players will nod and agree and we haven't even calculated the probabilities yet.  But Bruiser knows he needs a 22; he probably knows he gets a +8 on his roll, and he's going to look for additional bonuses (like a running start or using a statue as a battering ram).  That may not actually reflect what I think the odds ought to be if I carefully considered them, but it works pretty quickly, and if the situation changes (now Poindexter is trying to break down the door and Bruiser is holding it) it's really easy to modify on the fly - the DC is now 24 (stronger person holding) and Poindexter only has a +4 - he's also going to want to look for some situational modifiers. 

Quote from: deadDMwalking on July 20, 2022, 03:15:15 PM
Throughout this thread a number of people have indicated that they tend to think in probabilities.  In the case that you KNOW a probability that can be easy to do.  On the other hand, frequently in the game you're asked to create a situation in which you don't know what the probability ought to be.

Is throwing a grappling hook against a 40' tower significantly different than throwing it against a 20' tower?  If I have an 85% in grapple hooking, does that mean it applies equally to both situations?  Or is one of them 'normal' and I get a +20%/-20% in the other?  What does it mean if I have an 85% in a skill, but I'm also using the skill at -30% or -40%?

Most people have trouble thinking in probabilities, and comparing relative abilities of different people meaningfully is hard (as has been described above).  If I think that Bruiser the Door Buster has a 95% chance of breaking a door, and Poindexter is half as strong, do I think he should have a 45% chance, or 0%. Is there any skill involved or is it all attribute based?  What if Poindexter is trying to hold the door closed?

Assigning a fixed TN without considering any of the individuals and then letting them apply their relevant abilities tends to be easier for most people.  If I say that breaking down a door is a TN 20, and someone holding the door is usually a -4, but someone weak and frail only counts as a -2, a lot of players will nod and agree and we haven't even calculated the probabilities yet.  But Bruiser knows he needs a 22; he probably knows he gets a +8 on his roll, and he's going to look for additional bonuses (like a running start or using a statue as a battering ram).  That may not actually reflect what I think the odds ought to be if I carefully considered them, but it works pretty quickly, and if the situation changes (now Poindexter is trying to break down the door and Bruiser is holding it) it's really easy to modify on the fly - the DC is now 24 (stronger person holding) and Poindexter only has a +4 - he's also going to want to look for some situational modifiers.

I agree a lot of people don't understand probability. I don't blame them, it's not a simple topic. And I'm far from an expert, but I distinctly recall my university stats professor's rant about how probability is widely misunderstood and one of the most common misunderstandings is that you must have a significant number of samples for the whole idea of probability to have any meaning. n = 100 at a minimum.

So, for one-off events, like bashing a door down or things you might do a few times in a campaign, probability is a meaningless concept. The number you pick really doesn't matter much. People have a hard time wrapping their head around this. A single die roll is deterministic and its outcome is predicable, you just don't know it yet. So the best thing to do is treat one-off probabilities as a form of expression that emphasizes game fluff, setting, and character. Poindexter gets -40% penalty to bashing the door down because he's just that much of a weakling. Or, if you prefer negotiating for bonuses in d20 land, it's the same thing. It helps players create a clear image of the situation and their character.

For repeated events where a trend is observable, such as weapons use, probability starts to mean something. Performing a significant number of rolls, which individually may be deterministic, gives meaning to probability. However, repeated events like combat actions are normally very well covered by the rules with set bonuses and penalties and likely subject to extensive play testing to get the right feel. If attacking from behind gives you +50%, you will notice the benefit of such dishonorable tactics after a few sessions.

Quote from: rytrasmi on July 20, 2022, 04:19:34 PM
I agree a lot of people don't understand probability. I don't blame them, it's not a simple topic. And I'm far from an expert, but I distinctly recall my university stats professor's rant about how probability is widely misunderstood and one of the most common misunderstandings is that you must have a significant number of samples for the whole idea of probability to have any meaning. n = 100 at a minimum...

Even people who do understand probability fail to apply it correctly more than you would expect when eyeballing a course of action.   Take a group of statistics gurus in a room and give them a modest probability decision that they'll need about 30 to 60 seconds to rough calculate a ballpark answer to.  Make them answer in 5 or 10 seconds.  On average, they'll probably do better than most people, but they'll still be wrong a lot.  Which is why statisticians are sometimes surprised by the answers they get.

Of course, this doesn't apply to the simple stuff.  No one that gets basic probability is going to keep having their character do some risky course of action that's got in the neighborhood of a 25% chance, even when their off the cuff calculations are wrong and the chance is really 30% or 18%.  They know it's low, and low chances multiplied together become practically auto fail, quick.  People that don't understand probability can learn the same lesson a little slower via experience.  And then other people never do.  Plus, you've always got a few that are staying in character, and better at judging risks through criteria other than the game math, and sometimes they do better than anyone else when it comes to deciding to do risky thing X or not.  Finally, I've observed people who are really bad at probability but try to apply it anyway, and often talk themselves into a bad course of action that their common sense was screaming the whole time was a bad idea.  It takes all kinds.

Quote from: Jam The MF on July 15, 2022, 07:13:11 PM
Having a % Chance of Being Successful at "X", is a very natural way of explaining things.

Why haven't Percentile-Based Systems won out in a big way, in the RPG market?

Thanks in advance, for chiming in.

Most so-called "role-play gamers" have no idea how die mechanics work, or how die percentages work. They certainly do think the d20 is more shiny than the d100, that's for sure.

Quote from: Visitor Q on July 20, 2022, 09:43:26 AM
On other occasions there isn't one stat or characteristic or skill that is appropriate to teat against but a combination. 

This isn't specific to % systems; it happens in pretty much every game system.

Probability is just probability.  How you get there is more a matter of aesthetics than functionality.  That said, some randomizer mechanics just irritate me.  Dice pools, for example.  No reason why, I just don't like them.  Percentile systems are okay, but there's a couple of reasons they're not my favorite.

1)  Adding up two digit numbers is not particularly fun.  Just because I do tensor calculus as part of my job doesn't mean I want to do a lot of arithmetic as part of my recreation.
2)  Some percentile systems use small modifiers, which IMO don't make enough difference to be worth the trouble of doing them.  It's not really worth thinking about something just to get a 1% bonus.
3)  I find roll-under to be unintuitive.  And roll-over percentile moves away from the simplicity that is the approach's primary strength.
4)  I don't actually like probabilities to by immediately apparent.  Thinking about numbers takes my head right out of the game fiction.

None of these are deal-killer for a game to me, but I think enough folks share some of these views that there is not a widespread desire to switch to percentile systems.

Swinginess is a bell-curve vs linear system issue, not specific to percentile.  And the design of the rest of the system can fix this if wanted.

At the moment, I'm leaning towards systems where randomness has a smaller role.  My current game runs on d6+skill(usually 1-20, but 30 max)+modifiers (typically up to +/- 10 total)

Quote from: HappyDaze on July 21, 2022, 12:52:16 AM

Quote from: Visitor Q on July 20, 2022, 09:43:26 AM
On other occasions there isn't one stat or characteristic or skill that is appropriate to teat against but a combination. 

This isn't specific to % systems; it happens in pretty much every game system.

That was my point. Percentile systems are intuitively good for understanding the stakes and knowing success or failures, but when that becomes more complicated perhaps there are other solutions to expressing that.

Quote from: Steven Mitchell on July 20, 2022, 04:35:13 PM
Even people who do understand probability fail to apply it correctly more than you would expect when eyeballing a course of action.   Take a group of statistics gurus in a room and give them a modest probability decision that they'll need about 30 to 60 seconds to rough calculate a ballpark answer to.  Make them answer in 5 or 10 seconds.  On average, they'll probably do better than most people, but they'll still be wrong a lot.  Which is why statisticians are sometimes surprised by the answers they get.

Or perhaps set up a range of different castle walls and run sets of trials of throwing a grapple from various distances. You could then obtain a base probability, say 63% at 10 meters range for a 5 meter wall, with modifiers for distance and height, say +/- 2% per meter.

So, you have an accurate probability. Great. But that still doesn't matter much in a campaign where you grapple onto a castle wall once or twice. Your campaign would need to have the PCs grappling walls every day left and right for the 63% to be realized in game as a trend. A single attempt, or even a few attempts, won't elicit the 63%. Or perhaps numerous players from different campaigns would compare notes and discover that the grapple chance is pretty accurate as a whole. All that is a lot of trouble, so for rare events, pick a probability that sounds reasonable and be done with it.

Quote from: Steven Mitchell on July 20, 2022, 04:35:13 PM
Plus, you've always got a few that are staying in character, and better at judging risks through criteria other than the game math, and sometimes they do better than anyone else when it comes to deciding to do risky thing X or not.

This is the best way, as far as I'm concerned. Look at the risk through the lens of your character. Bjorn the Barbarian is not going to worry about probabilities. At best, he knows that the last 5 guys who attempted this stunt all died, but rumor tells of a great man long ago who once succeeded. A good GM would award Bjorn a bonus for role play to encourage this kind of behavior at the table. A meta-carrot for the players who worry about the numbers.

No one wants to think about numbers. Think about it.

Quote from: deadDMwalking on July 20, 2022, 03:15:15 PM
I agree a lot of people don't understand probability. I don't blame them, it's not a simple topic. And I'm far from an expert, but I distinctly recall my university stats professor's rant about how probability is widely misunderstood and one of the most common misunderstandings is that you must have a significant number of samples for the whole idea of probability to have any meaning. n = 100 at a minimum.

So, for one-off events, like bashing a door down or things you might do a few times in a campaign, probability is a meaningless concept.

That's not exactly true. Mathematician, Richard von Mises, who has an award named after him, specified a distinction between Class Probability and Case Probability. You've probably heard that in a room full of 23 randomly selected people, there is > 50% chance that two will share the same birthday. That was von Mises that came up with that. What your stats professor is referring to is strictly Class Probability, and it is true that the rules of Class Probability do not generally translate to Case Probability. It is not true that Case Probability is a meaningless concept.

And I can give an example of why that matters and is not just playing word games with definitions. Consider the finitely iterated Prisoners Dilemma. Backwards induction tells us that the winning strategy is defect. It doesn't pan out in reality. Unfortunately it's common that when professors, mathematicians, and scientists, the explanation is always, "Just proves people are irrational," and there is a litany of serious problems with that dismissal. Especially when there's a fairly easy explanation. Like simply understanding that no matter what backwards induction tells us, that because the players in the prisoners dilemma are allowed to choose, it's possible they will cooperate. That is to say, there is a non-zero probability in what is essentially a one-off event (since later iterations of the game can be informed by prior ones, the various iterations do not form a class). That non-zero probability means that there is a combination of expected future iterations and expected rewards for cooperation for which there is rational indifference, and then beyond that point it's actually rational to cooperate rather than defect.

For an almost innocuous fact of p > 0 flipping a major conclusion in game theory on its head, I'd call that very meaningful. Once you get that camel's nose under the tent, it opens the field up from there. Like in an RPG, I might not know the probability of bashing down a door. But I can logically and rationally surmise that drinking a potion of strength should help matters boosting the probability by some amount greater than zero. You follow this sort of logic to its fruition, you can derive an entire system of relative probabilities--strictly ordinal, perhaps--but enough of one that for consistency's sake the DM and the game system ought to act as if the singular case of bashing in a door has percent chance attached someway somehow. It's usually just easier to give in and treat it like regular class probability.

Quote from: Mishihari on July 21, 2022, 02:57:32 AM
Dice pools, for example.  No reason why, I just don't like them.  Percentile systems are okay, but there's a couple of reasons they're not my favorite.

My central thesis here has been that arbitrary likes/dislikes are probably the only honest answers to the question posed. As soon as people start providing reasons, I have yet to see reasons that don't fall apart under scrutiny. You managed to nail the big four on this topic:

Quote1)  Adding up two digit numbers is not particularly fun.  Just because I do tensor calculus as part of my job doesn't mean I want to do a lot of arithmetic as part of my recreation.

I pointed this out in an earlier post here. If you're adding multiples of 10, that's not really two digit addition. Neither is adding a single digit number. The percentile games I actually play on a regular basis mostly use multiples of 10 as modifiers, but have a small number of modifiers that are multiples of 5, and then also single-digit modifiers. The fact is, there is a window which renders these criticisms moot, and there are percentile games that fit that window.

Quote2)  Some percentile systems use small modifiers, which IMO don't make enough difference to be worth the trouble of doing them.  It's not really worth thinking about something just to get a 1% bonus.

Small modifiers are absolutely significant when dealing with small probabilities. In actual percentile RPGs I play on a regular basis, small modifiers can often modify the die roll itself, rather than the target number, the primary effect of which is to heavily skew the probability of critical success and/or failure.

Quote3)  I find roll-under to be unintuitive.  And roll-over percentile moves away from the simplicity that is the approach's primary strength.

There are two reasons I find this point to be silly.

The first reason is, I think it lacks perspective. People who say they find roll-under counter-intuitive are perfectly happy doing something like, oh, rolling a d20 and having to add a base attack bonus each and every time to try and get a high result. If you look at normie games--non-RPGs and games that are not RPG-adjacent--you don't see this. Maybe "intuitive" isn't the reason why monopoly doesn't give the race car 2d6+4 movement on that player's turn. It's because it looks inelegant and requires an extra math step. But at the end of the day, among normie games, you're more likely to find Roll-under systems and matrix or THAC0 style systems than roll die plus base. I think that should challenge gamers notions of what is or isn't intuitive in the broader context.

But the second and more clear cut reason is, higher, lower, up, down, addition, subtraction, all of these differences can be flipped by re-framing the mechanic. In AD&D, you might have a -2 Dex bonus. Minus? Bonus? Cue mentally obese gamer saying That's Counterintuitive. And it's like, yeah, fucko. The dude is so nimble, anyone who wants to hit him has a -2. Sounds pretty fucking intuitive to me. But but... his +3 ring of protection. Surely you can't have plus and minus both make him harder to hit. Sure you can. The +3 magic bonus is added to your target number when trying to hit the guy. Now you got to roll 3 points higher.

With rollunder, instead of saying, "You gotta roll under your fuck shit up skill to hit the guy," you pin the roll on the defender saying, "You got to roll over that guy's fuck shit up skill to dodge the blow." Presto chango, now you've got a roll-over system with all the same identical statistics and even dice mechanics as ye olde roll-under system.

Quote4)  I don't actually like probabilities to by immediately apparent.  Thinking about numbers takes my head right out of the game fiction.

And this is never ever ever in any game with any GM at any table at any time anywhere ever the case. Simply because GMs are not obliged to inform players of all modifiers in play. Even if the GM regularly does, because the GM can always choose not to, there is a probability greater than zero that the GM will hold back secret modifiers. And that means you have no idea if the roll you're making right now happens to be the one in a thousand where there's something you don't know. Meaning you never actually know the probability.


None of this means you have to like percentile systems. The point is these reasons aren't the actual reasons. I mostly just want to use all the damn dice I bought and paid for.

Quote from: Lunamancer on July 21, 2022, 10:37:42 AM
That's not exactly true. Mathematician, Richard von Mises, who has an award named after him, specified a distinction between Class Probability and Case Probability. You've probably heard that in a room full of 23 randomly selected people, there is > 50% chance that two will share the same birthday. That was von Mises that came up with that. What your stats professor is referring to is strictly Class Probability, and it is true that the rules of Class Probability do not generally translate to Case Probability. It is not true that Case Probability is a meaningless concept.

And I can give an example of why that matters and is not just playing word games with definitions. Consider the finitely iterated Prisoners Dilemma. Backwards induction tells us that the winning strategy is defect. It doesn't pan out in reality. Unfortunately it's common that when professors, mathematicians, and scientists, the explanation is always, "Just proves people are irrational," and there is a litany of serious problems with that dismissal. Especially when there's a fairly easy explanation. Like simply understanding that no matter what backwards induction tells us, that because the players in the prisoners dilemma are allowed to choose, it's possible they will cooperate. That is to say, there is a non-zero probability in what is essentially a one-off event (since later iterations of the game can be informed by prior ones, the various iterations do not form a class). That non-zero probability means that there is a combination of expected future iterations and expected rewards for cooperation for which there is rational indifference, and then beyond that point it's actually rational to cooperate rather than defect.

For an almost innocuous fact of p > 0 flipping a major conclusion in game theory on its head, I'd call that very meaningful. Once you get that camel's nose under the tent, it opens the field up from there. Like in an RPG, I might not know the probability of bashing down a door. But I can logically and rationally surmise that drinking a potion of strength should help matters boosting the probability by some amount greater than zero. You follow this sort of logic to its fruition, you can derive an entire system of relative probabilities--strictly ordinal, perhaps--but enough of one that for consistency's sake the DM and the game system ought to act as if the singular case of bashing in a door has percent chance attached someway somehow. It's usually just easier to give in and treat it like regular class probability.

Interesting. (I think you were quoting me and not deadDMwalking.)

I'm struggling with the idea of Case Probability. I recall that a popular statistician was lambasted for predicting Clinton to win over Trump. Of course, he was wrong. His reply was that he only gave Clinton a 70% chance, so he wasn't actually wrong. This kind of thing is impossible to test. In other words, had he said 90% instead of 70% what difference would it have made?

It would seem that if you're building a unique Case Probability out of bits and pieces of things that have well-understood probabilities, then the ultimate Case Probability is certainty (i.e., you have total information). Or maybe I'm misunderstanding the concept.

Quote from: Lunamancer on July 21, 2022, 12:56:28 PM
With rollunder, instead of saying, "You gotta roll under your fuck shit up skill to hit the guy," you pin the roll on the defender saying, "You got to roll over that guy's fuck shit up skill to dodge the blow." Presto chango, now you've got a roll-over system with all the same identical statistics and even dice mechanics as ye olde roll-under system.

Specifically for roll-under with degrees of success (usually based on 10 under), I think people struggle. 

For example, the TN is 75, and you roll a 49.  Obvious that's a success.  But how many degrees?  59 is 1, 69 is 2, so a total of 2 'degrees'.  If it matters, you beat the TN by 26. 

I think it is easier to take your 75 skill as a base and roll/add against a TN of 100.  In the mirror image of this, rolling a 51 and adding to 75 gives you 126.  Drop the hundreds digit and you know you exceeded the TN by 26 and you can look at the 10s digit and know that it counts as 2 full degrees of success. 

Boils down to a matter of taste.

There are many pros and cons, but they also boil down to personal tastes.

A d100 has very clear chances, a dice pool is easy to add modifiers, a d20 is nice and familiar, a d6 is readily available everywhere, 3d6 has a nice bell curve, etc.

Some people prefer roll high, others roll low. Some hate the idea of "blackjack" (which is perfect for d100 IMO), etc. I find Target 20 awesome but also find descending AC counterintuitive.

I like d100 systems. CoC is great of course, Unknown Armies is cool, Mythras has interesting options, and so on.

Quote from: deadDMwalking on July 21, 2022, 03:52:28 PM

Quote from: Lunamancer on July 21, 2022, 12:56:28 PM
With rollunder, instead of saying, "You gotta roll under your fuck shit up skill to hit the guy," you pin the roll on the defender saying, "You got to roll over that guy's fuck shit up skill to dodge the blow." Presto chango, now you've got a roll-over system with all the same identical statistics and even dice mechanics as ye olde roll-under system.

Specifically for roll-under with degrees of success (usually based on 10 under), I think people struggle. 

For example, the TN is 75, and you roll a 49.  Obvious that's a success.  But how many degrees?  59 is 1, 69 is 2, so a total of 2 'degrees'.  If it matters, you beat the TN by 26. 

I think it is easier to take your 75 skill as a base and roll/add against a TN of 100.  In the mirror image of this, rolling a 51 and adding to 75 gives you 126.  Drop the hundreds digit and you know you exceeded the TN by 26 and you can look at the 10s digit and know that it counts as 2 full degrees of success.

Some games go with the blackjack method where the tens value of a successful roll-under check is the success level. In this case, if you need a 75 or lower and roll a 49, you have 4 success levels. Yes, this means you want to roll as high as possible without exceeding the target number. It's a very quick way to do it, and works especially well when degrees of failure are not relevant.

Quote from: Lunamancer on July 21, 2022, 12:56:28 PM

Quote from: Mishihari on July 21, 2022, 02:57:32 AM
Dice pools, for example.  No reason why, I just don't like them.  Percentile systems are okay, but there's a couple of reasons they're not my favorite.

My central thesis here has been that arbitrary likes/dislikes are probably the only honest answers to the question posed. As soon as people start providing reasons, I have yet to see reasons that don't fall apart under scrutiny. You managed to nail the big four on this topic:

Quote1)  Adding up two digit numbers is not particularly fun.  Just because I do tensor calculus as part of my job doesn't mean I want to do a lot of arithmetic as part of my recreation.

I pointed this out in an earlier post here. If you're adding multiples of 10, that's not really two digit addition. Neither is adding a single digit number. The percentile games I actually play on a regular basis mostly use multiples of 10 as modifiers, but have a small number of modifiers that are multiples of 5, and then also single-digit modifiers. The fact is, there is a window which renders these criticisms moot, and there are percentile games that fit that window.

Quote2)  Some percentile systems use small modifiers, which IMO don't make enough difference to be worth the trouble of doing them.  It's not really worth thinking about something just to get a 1% bonus.

Small modifiers are absolutely significant when dealing with small probabilities. In actual percentile RPGs I play on a regular basis, small modifiers can often modify the die roll itself, rather than the target number, the primary effect of which is to heavily skew the probability of critical success and/or failure.

Quote3)  I find roll-under to be unintuitive.  And roll-over percentile moves away from the simplicity that is the approach's primary strength.

There are two reasons I find this point to be silly.

The first reason is, I think it lacks perspective. People who say they find roll-under counter-intuitive are perfectly happy doing something like, oh, rolling a d20 and having to add a base attack bonus each and every time to try and get a high result. If you look at normie games--non-RPGs and games that are not RPG-adjacent--you don't see this. Maybe "intuitive" isn't the reason why monopoly doesn't give the race car 2d6+4 movement on that player's turn. It's because it looks inelegant and requires an extra math step. But at the end of the day, among normie games, you're more likely to find Roll-under systems and matrix or THAC0 style systems than roll die plus base. I think that should challenge gamers notions of what is or isn't intuitive in the broader context.

But the second and more clear cut reason is, higher, lower, up, down, addition, subtraction, all of these differences can be flipped by re-framing the mechanic. In AD&D, you might have a -2 Dex bonus. Minus? Bonus? Cue mentally obese gamer saying That's Counterintuitive. And it's like, yeah, fucko. The dude is so nimble, anyone who wants to hit him has a -2. Sounds pretty fucking intuitive to me. But but... his +3 ring of protection. Surely you can't have plus and minus both make him harder to hit. Sure you can. The +3 magic bonus is added to your target number when trying to hit the guy. Now you got to roll 3 points higher.

With rollunder, instead of saying, "You gotta roll under your fuck shit up skill to hit the guy," you pin the roll on the defender saying, "You got to roll over that guy's fuck shit up skill to dodge the blow." Presto chango, now you've got a roll-over system with all the same identical statistics and even dice mechanics as ye olde roll-under system.

Quote4)  I don't actually like probabilities to by immediately apparent.  Thinking about numbers takes my head right out of the game fiction.

And this is never ever ever in any game with any GM at any table at any time anywhere ever the case. Simply because GMs are not obliged to inform players of all modifiers in play. Even if the GM regularly does, because the GM can always choose not to, there is a probability greater than zero that the GM will hold back secret modifiers. And that means you have no idea if the roll you're making right now happens to be the one in a thousand where there's something you don't know. Meaning you never actually know the probability.


None of this means you have to like percentile systems. The point is these reasons aren't the actual reasons. I mostly just want to use all the damn dice I bought and paid for.

I'll reply to your points in order ...

(a) I don't think dice preferences are entirely irrational.  Some preferences make sense.  Quicker is better than slower.  Less work is better than more.  There are solid reasons to prefer obscuring rather than revealing probabilities or vice versa to support a preferred style of play.

(1)   It's not a big difference, but manipulating two digit numbers is verifiably more time, work, etc than 1 digit numbers.  It doesn't matter to everyone, but for those who do care it's a pretty logical reason

(2)   In a percentile pass/fail roll, a 1% modifier will change the result from fail to pass or the other way around once in every 100 rolls, on average.  That's not often enough for me to want to make the slight effort to add it in.  Admittedly, not all percentile systems use modifiers this small, but if, frex, your smallest modifier is 5%, you're better off using a d20.

(3)   I find roll over systems to be more intuitive because in so many things, more is better.  I'd rather have more money, more cars, more square footage in my house.  Higher is better on a roll is just what I expect.

(4)   Sure, sometimes there are hidden modifiers.   IME as a GM, more often there are not.  As I said, I prefer not to know precise probabilities, and that's a tiny bit harder with percentile than other single die rolls.  I prefer add up 2 or more dice for this reason

Quote from: Mishihari on July 21, 2022, 05:17:56 PM
I'll reply to your points in order ...

(a) I don't think dice preferences are entirely irrational.  Some preferences make sense.  Quicker is better than slower.  Less work is better than more.  There are solid reasons to prefer obscuring rather than revealing probabilities or vice versa to support a preferred style of play.

(1)   It's not a big difference, but manipulating two digit numbers is verifiably more time, work, etc than 1 digit numbers.  It doesn't matter to everyone, but for those who do care it's a pretty logical reason

(2)   In a percentile pass/fail roll, a 1% modifier will change the result from fail to pass or the other way around once in every 100 rolls, on average.  That's not often enough for me to want to make the slight effort to add it in.  Admittedly, not all percentile systems use modifiers this small, but if, frex, your smallest modifier is 5%, you're better off using a d20.

(3)   I find roll over systems to be more intuitive because in so many things, more is better.  I'd rather have more money, more cars, more square footage in my house.  Higher is better on a roll is just what I expect.

(4)   Sure, sometimes there are hidden modifiers.   IME as a GM, more often there are not.  As I said, I prefer not to know precise probabilities, and that's a tiny bit harder with percentile than other single die rolls.  I prefer add up 2 or more dice for this reason

Yes. Not everything expressed as "feel" is irrational.  It's not universal or even consistent across everyone, but where people place value has subtle differences that add up. Some of those differences are not so subtle with certain gamers.  Since gaming is a shared activity, it's not only about what I like but what I'm willing to put up with in others.  Explaining for the umpteenth time that for this roll you want high and that roll you want low--is well, not something that I ever enjoyed, and whatever tolerance I had for it as a necessary cost of running the game has long since evaporated.  Which is why I don't mind roll under as a player nearly so much as a GM (even though I also have a very mild irrational prejudice against roll under strictly from a feel perspective, but not so much that I can't happily play a game that uses it when it's run by someone else).

There is one concrete minor benefit to roll under that hasn't been listed yet:  If the checks are roll under and the effects are roll high (e.g. damage dice), then it discourages players using biased dice.  Works better in systems where it is all the same dice type, such as Fantasy Hero.  Of course, it's easier to simply boot the players that are deliberately using biased dice.

Quote from: Steven Mitchell on July 21, 2022, 05:43:54 PM
If the checks are roll under and the effects are roll high (e.g. damage dice), then it discourages players using biased dice.  Works better in systems where it is all the same dice type

Ha, only if the players typically own only one die of the given type. IME it's a pretty rare player that both (1) only has a single d20 and (2) brings their own dice.

Quote from: rytrasmi on July 21, 2022, 02:39:38 PM
Interesting. (I think you were quoting me and not deadDMwalking.)

Yeah, sorry about that. I'm usually squeezing posts in during a short break. I might have even been known to misspell reciprocal.

QuoteI'm struggling with the idea of Case Probability. I recall that a popular statistician was lambasted for predicting Clinton to win over Trump. Of course, he was wrong. His reply was that he only gave Clinton a 70% chance, so he wasn't actually wrong. This kind of thing is impossible to test. In other words, had he said 90% instead of 70% what difference would it have made?

The issue is more of whether or not what we're talking about is an element of a class. If instead of an election it were a lottery with 5 winners drawn and 100 tickets, if I were to hold up an individual ticket and claim it's 5% likely to win, is that an unreasonable claim? If that ticket turns out to be one of the winners, will there be any lambasting? Will anyone be laughing, "Haha, read it and weep, asshole. The ticket you said was 95% likely to lose just won. So suck it!"? If I had said it was 90% likely to win rather than 5%, would I have been more right or less? Would any of it be falsifiable by experience?

When the intellectual heavyweights who studied this drilled down to the heart of the matter, the difference came down to whether you had deterministic causality or non-deterministic causality. Going back to the Prisoners Dilemma, backwards induction is assuming deterministic causality. Because game theory sez defect on the last step, therefore when you're on the second to last step you can rule out future cooperation, therefore no good reason to cooperate now, so on and so forth all the way back to step 1. Non-deterministic causality is the insight that humans can choose to do other than what game theory tells them. Thus the non-zero probability, which in turn changes future expected payoffs and therefore influences the earlier states.

Elections fall under case probability because people choose who to vote for. Even though there's a ton of science behind polling and campaigning, Spend X dollars in Y market with message ABC and net Z votes. That sort of thing. But just because a pattern has held historically does not mean voters are obliged to keep turning out in the same pattern. There will always be some small deviation from the pattern. And some probability p > 0 of a large enough regularity to overturn the results of an election.

Doors from old school style dungeon crawls, unless otherwise noted, are always stuck, never locked, and won't stay open without being wedged or spiked. Those doors are elements of a class. So much so that in AD&D, your strength score actually told you what your probability of opening a door was. Like no one even asked the door how difficult it felt like being. Doors were that standardized. They are definitely elements of a class.

QuoteIt would seem that if you're building a unique Case Probability out of bits and pieces of things that have well-understood probabilities, then the ultimate Case Probability is certainty (i.e., you have total information). Or maybe I'm misunderstanding the concept.

Even though we normally don't think of it this way, probability by definition means our knowledge concerning the content of a proposition is deficient. We do not know everything for which would be required for a definite decision between true and not true. But on the other hand we do know something about it.

Class probability means we know or assume to know, with regard to the problem concerned, everything about the behavior of a whole class of events of phenomena, but about the actual singular events or phenomena we know nothing but that they are elements of this class.

Case probability means we know, with regard to a particular event, some of the factors which determine its outcome, but there are other determining factors about which we know nothing. So in case probability you actually have a greater deficiency in knowledge than in class probability.

Quote from: Mishihari on July 21, 2022, 05:17:56 PM
(a) I don't think dice preferences are entirely irrational.  Some preferences make sense.  Quicker is better than slower.  Less work is better than more.  There are solid reasons to prefer obscuring rather than revealing probabilities or vice versa to support a preferred style of play.

(1)   It's not a big difference, but manipulating two digit numbers is verifiably more time, work, etc than 1 digit numbers.  It doesn't matter to everyone, but for those who do care it's a pretty logical reason

I have a bigger point in all this, but my response to this, perhaps our disagreement, supports my bigger point.

As soon as got to the part where you say "quicker is better than slower" red flags already started going up. And it didn't take long for gut feeling to be vindicated. If you want to say manipulating two digit numbers in general is verifiably more time, that's one thing. But it's not applicable to when you're only manipulating one digit--the 10's digit--because modifiers are multiples of 10. That's not a verifiable truth. Whether you agree or disagree, the point is it's disputed and that there is no objective quicker vs slower that's being compared here. It sounds like a nice, indisputable statement. But it falls apart just like all the other reasons under scrutiny.

Quote(2)   In a percentile pass/fail roll, a 1% modifier will change the result from fail to pass or the other way around once in every 100 rolls, on average.  That's not often enough for me to want to make the slight effort to add it in.  Admittedly, not all percentile systems use modifiers this small, but if, frex, your smallest modifier is 5%, you're better off using a d20.

Here again, you claim to be responding to my points but are not. I had two separate points on this, and one of those points had nothing to do with probability at all. So it's non responsive to come back with a probability argument. The other one had to do with shifts in probabilities that already had a low base chance, like criticals, and the possibility of zeroing them out in some cases. The incidence of criticals are rarely ever statistically significant. But their magnitude when they do come up makes them meaningful. That's kind of the whole point of them. And what I had pointed out is that eliminating them is obviously meaningful.

But now that I'm repeating it, I think criticals by themselves disprove your point. The same gamers who will agree "Less than 5% is insignificant, Just use d20" also like criticals. 3E called for confirming die rolls just to make sure probabilities for getting criticals could shift in units smaller than 5% increments. Something here just doesn't add up. Because it's fake rationale.

Quote(3)   I find roll over systems to be more intuitive because in so many things, more is better.  I'd rather have more money, more cars, more square footage in my house.  Higher is better on a roll is just what I expect.

Non-responsive. I said you have to roll higher than the other guy's fuck shit up skill if you want to dodge his attack. Higher is better. And we preserve his skill rating as being a nice, intuitive percent chance to hit.

So here's my bigger point. If I were to ask for a show of hands, how many gamers out there feel like the d100 system is not your cup of tea. Now of those of you with your hand up, you can put your hand down if you have some reason outside the standard 4 that keep getting repeated. Keep your hand up any one of the four, any combination of the four, or if all four are really what bothers you about d100 systems.

Now suppose I propose we play an RPG where every one of those four concerns are addressed, sort of like I've been explaining. You will never have to perform two-digit addition or subtraction. There will be modifiers that are not multiples of 5 or 10. Small percentages will have a significant impact on the game. You will never know for sure your exact odds of success--that information will never be there for you to break your immersion. And when you roll, higher is better. But it's still going to be a percentile system.

I'd be shocked if 1 out of every dozen gamers who still had their hands up at the beginning of the paragraph would take me up on such a game. Because these reasons are all bullshit. Some people just don't like d100 systems for no good reason. And that's perfectly fine. You yourself addressed my comments point for point but ignored 3 out of 4 of my bullet points entirely. Why? Why would you do that? Because none of this discussion really has anything at all to do with reason.

Just goes to show it really is all about the numbers.

Quote from: hedgehobbit on July 19, 2022, 04:45:05 PM

Quote from: BoxCrayonTales on July 19, 2022, 04:11:30 PMHow familiar are you with BRP? It already addresses the stuff you're bringing up. Or at least the 4e rulebook does. The SRD is crap.

I'm fairly familiar with older versions. Stormbringer was the 2nd campaign I ever ran and my Runequest game was my longest campaign before D&D 3e came out. I understand the BRP already does similar things to what I was talking about, but I find that converting success values into numbered successes, rather than named values, is much more flexible (as you can see in the James Bond 007 RPG). So instead of having a Attack and Defense Matrix like on page 193 of BRP 4e, you just subtract the target's successes from the attacker's. Plus, by having successes listed in numerical values, you can have a list of things to spend those successes on in resolution. For example, 1 success would do damage, but with 2 successes, you could do damage twice, or change the hit location and do damage, or trade both in for a Disarm effect, etc. I prefer systems where you spend successful rolls over system where you have to declare your special action (Called Shots, Disarm, etc) in advance as declaring in advance slows the game down.

For me it is all about speed of resolution and flexibility.

The Pow vs Pow table can work for that too. I forget what page it's on and don't have the book with me at this moment, but it lets you compare the skills of the attacker and defender and reduce it to just one roll.

Honestly, the problem with a lot of these systems is that they always make combat more complex than it needs to be and devote much of their rules to combat. To be entirely honest, I think you can heavily simplify the combat similar to what's been done with True20.

Quote from: BoxCrayonTales on July 22, 2022, 09:21:45 AM

Quote from: hedgehobbit on July 19, 2022, 04:45:05 PM

Quote from: BoxCrayonTales on July 19, 2022, 04:11:30 PMHow familiar are you with BRP? It already addresses the stuff you're bringing up. Or at least the 4e rulebook does. The SRD is crap.

I'm fairly familiar with older versions. Stormbringer was the 2nd campaign I ever ran and my Runequest game was my longest campaign before D&D 3e came out. I understand the BRP already does similar things to what I was talking about, but I find that converting success values into numbered successes, rather than named values, is much more flexible (as you can see in the James Bond 007 RPG). So instead of having a Attack and Defense Matrix like on page 193 of BRP 4e, you just subtract the target's successes from the attacker's. Plus, by having successes listed in numerical values, you can have a list of things to spend those successes on in resolution. For example, 1 success would do damage, but with 2 successes, you could do damage twice, or change the hit location and do damage, or trade both in for a Disarm effect, etc. I prefer systems where you spend successful rolls over system where you have to declare your special action (Called Shots, Disarm, etc) in advance as declaring in advance slows the game down.

For me it is all about speed of resolution and flexibility.

The Pow vs Pow table can work for that too. I forget what page it's on and don't have the book with me at this moment, but it lets you compare the skills of the attacker and defender and reduce it to just one roll.

Honestly, the problem with a lot of these systems is that they always make combat more complex than it needs to be and devote much of their rules to combat. To be entirely honest, I think you can heavily simplify the combat similar to what's been done with True20.

I actually think it was a good move for later editions of CoC to dispense with the contest table. It was definitely a legacy feature from a time when RPGs were frequently needlessly complicated. The benefits of hindsight, eh?