Quote from: Omega;1114396What sort of dice are being used? Same as in BRP or something else?

We´re using D100 as this was the default, but using a D20 wont make any difference even in play, as skills advance in steps of 5 (5, 10, 15, 20, etc).
As somebody wrote, I could probably work out the statistics for a D10, or even smaller dice, and still get an idea, it´s just less granular (is that the word?).

If going the d20 route and stats step in 5s then it is pretty simple to figure the base chance and then from there work out the chance after modifiers. Same for any threshold that has to be met. It all breaks down into basic percentile chances.

Going smaller dice indeed removes some spread. But might make result tables easier. A bit of give and take as ever. Somilar to how using the percentile d6 system shortens the possible outcomes but you still have a fair spread of 60 or so results instead of 100.

Quote from: Omega;1114395And Roll under in absolutely no way eliminates modifiers.

It does if you don't use proficiencies and ignore things like task difficulty or situational modifiers, etc. Not my cup of tea, though.

Quote from: zx81;1114398We´re using D100 as this was the default, but using a D20 wont make any difference even in play, as skills advance in steps of 5 (5, 10, 15, 20, etc).
As somebody wrote, I could probably work out the statistics for a D10, or even smaller dice, and still get an idea, it´s just less granular (is that the word?).

Oh, that's really simple then. You just have to divide the BRP skill % by 5 for d20, or 10 for d10 to get the Roll Under value. You don't even need to account for the impact of opposed rolls on probability, since that gets handled when you roll and compare results. You just need the skill values.

% to d20
5% = 1
10% = 2
15% = 3
20% = 4
25% = 5
30% = 6
35% = 7
40% = 8
45% = 9
50% = 10
55% = 11
60% = 12
65% = 13
70% = 14
75% = 15
80% = 16
85% = 17
90% = 18
95% = 19
100% = 20

% to d10
10% = 1
20% = 2
30% = 3
40% = 4
50% = 5
60% = 6
70% = 7
80% = 8
90% = 9
100% = 10

Quote from: VisionStorm;1114351The issue with "roll under" systems is that they complicate opposed rolls and tend to favor high Attributes/Ability Scores above actual skill (which is the opposite of real life)--specially in old D&D, where you could get a 90% success rate just by getting lucky during character creation and scoring an 18.

Quote from: VisionStorm;1114390And it tends to rely too much on high Attributes/Ability Scores over actual training, which undermines skills and assumes natural ability as the overriding factor to perform all actions.

I'm a little confused by what you mean in terms of 'training'/'skill', could you unpack this? At least in GURPS (vs. roll-under D&D attributes for instance) your skill levels (training) have their own individually improved ratings, which if you are proficient are almost always better than your base attribute scores (and particularly, if you are working from default you suffer at least a -4 penalty to your base ability, not counting circumstantial modifiers like extra time taken/calm conditions/etc.). Your complaint from that perspective appears to be valid with regards to D&D, but also seems to me not an inherent issue with roll-under, but rather a specific implementation of it.

Quote from: VisionStorm;1114390Roll Under is more simple as long as you're willing to deal with its flaws and limitations. But the moment you want it to do more than simple Knowledge checks or similar ability checks that can be rolled unopposed its simplicity starts breaking apart.

I mean, specifically bell-curve roll-under does absolutely have limitations and flaws (most particularly with scaling), but it also has its benefits as well and I do consider it fairly 'realistic' in terms of similarity to real-life skill/training. I also consider it quite simple even with modifiers, as even if you're not straight rolling against the number written on your sheet modifiers are simply applied to the skill or attribute level rather than the roll itself. I feel it's easier for 'greenhorn' players to understand their general odds of success that way, without having to understand the DC system or what traditional difficulties / TN's might be in a given system for a given action.

I also know that it's partially just a taste/preference thing, beyond the mechanics spread. Roll-over/roll-under always seems to be quite divisive in the roleplaying hobby... however, I do firmly believe roll-under can be implemented effectively for those it appeals to. It's not perfect for everything, but really what dice mechanic is?

Quote from: VisionStorm;1114414It does if you don't use proficiencies and ignore things like task difficulty or situational modifiers, etc. Not my cup of tea, though.



Oh, that's really simple then. You just have to divide the BRP skill % by 5 for d20, or 10 for d10 to get the Roll Under value. You don't even need to account for the impact of opposed rolls on probability, since that gets handled when you roll and compare results. You just need the skill values.

% to d20
5% = 1
10% = 2
15% = 3
20% = 4
25% = 5
30% = 6
35% = 7
40% = 8
45% = 9
50% = 10
55% = 11
60% = 12
65% = 13
70% = 14
75% = 15
80% = 16
85% = 17
90% = 18
95% = 19
100% = 20

% to d10
10% = 1
20% = 2
30% = 3
40% = 4
50% = 5
60% = 6
70% = 7
80% = 8
90% = 9
100% = 10

Yes, I know how to convert d20 to d100, but my question was about the probabilities for different outcomes in an roll-high-under-mechanic similar to BRP.
Theres got to be a chart listing the probabilities of different outcomes in the BRP opposed rolls system somewhere.

Quote from: Antiquation!;1114419I'm a little confused by what you mean in terms of 'training'/'skill', could you unpack this? At least in GURPS (vs. roll-under D&D attributes for instance) your skill levels (training) have their own individually improved ratings, which if you are proficient are almost always better than your base attribute scores (and particularly, if you are working from default you suffer at least a -4 penalty to your base ability, not counting circumstantial modifiers like extra time taken/calm conditions/etc.). Your complaint from that perspective appears to be valid with regards to D&D, but also seems to me not an inherent issue with roll-under, but rather a specific implementation of it.


I mean, specifically bell-curve roll-under does absolutely have limitations and flaws (most particularly with scaling), but it also has its benefits as well and I do consider it fairly 'realistic' in terms of similarity to real-life skill/training. I also consider it quite simple even with modifiers, as even if you're not straight rolling against the number written on your sheet modifiers are simply applied to the skill or attribute level rather than the roll itself. I feel it's easier for 'greenhorn' players to understand their general odds of success that way, without having to understand the DC system or what traditional difficulties / TN's might be in a given system for a given action.

I also know that it's partially just a taste/preference thing, beyond the mechanics spread. Roll-over/roll-under always seems to be quite divisive in the roleplaying hobby... however, I do firmly believe roll-under can be implemented effectively for those it appeals to. It's not perfect for everything, but really what dice mechanic is?

Yeah, most of this probably applies more from a D&D perspective, since that's the Roll Under mechanic I'm most familiar with. I never got around playing GURPS, and only read some of the books years ago, so I'm fuzzy on the details. I also forgot to consider BRP, since I was thinking in terms of d20 rolls, rather than d100/%, and I only played CoC briefly decades ago. But most of my argument falls apart if the Roll Under value is primarily determined by skill/training (which would be my preference) rather than attributes.

At that point it becomes more an issue of preference, though I'd still argue that opposed rolls are probably more straightforward with Roll+Mod mechanics rather than Roll Under. But at the end of the day a lot of these mechanical differences are a matter of give & take. Some mechanics work better for certain purposes but have set backs in other areas. One mechanic might be simpler or emphasize play speed, but may also lack specificity, or a bell curve, etc.

It depends on your preferences or what you want to emphasize in your system.

Quote from: zx81;1114424Yes, I know how to convert d20 to d100, but my question was about the probabilities for different outcomes in an roll-high-under-mechanic similar to BRP.
Theres got to be a chart listing the probabilities of different outcomes in the BRP opposed rolls system somewhere.

I'm not sure what you mean by "probabilities for different outcomes". You mean like degrees of success? Maybe I'm missing something since I'm not terribly familiar with BRP.

Quote from: VisionStorm;1114425Yeah, most of this probably applies more from a D&D perspective, since that's the Roll Under mechanic I'm most familiar with.

Thanks for explaining, that's fair! That seemed to be where you're coming from, and in that context I absolutely agree with all your points. There is little subtlety in the various D&D versions of roll-under (or at least, all those which I am familiar with). I'm also not a big fan of any of the various skill implementations D&D has received over the years either, so to me it's become rather irreconcilable; not to mean that any of the roll+add systems have been non-functional, but rather that the way skill points and levels interact has always left a sour taste.

Quote from: VisionStorm;1114425I never got around playing GURPS, and only read some of the books years ago, so I'm fuzzy on the details. I also forgot to consider BRP, since I was thinking in terms of d20 rolls, rather than d100/%, and I only played CoC briefly decades ago. But most of my argument falls apart if the Roll Under value is primarily determined by skill/training (which would be my preference) rather than attributes.

I generally dislike the BRP roll-under system, and I'm not entirely sure why. It's a bit more palatable in Mythras, but generally the whole mechanism comes across as overly fiddly despite how often it's lauded as simple and straightforward (which, on the surface level, is true). I dislike skills increasing by a handful of percentiles, and amounts left to chance, even if it might come across as more believable / 'realistic' for some. Thinking back, I am also not a fan of the way difficulties are handled either in the + or - x%, or the alternative method with doubling/halving percentage chance (the former feels uncharitable towards laypersons in a given skill; the latter, towards experts); plus, skills above 100 have always been janky as shit.

Quote from: VisionStorm;1114425At that point it becomes more an issue of preference, though I'd still argue that opposed rolls are probably more straightforward with Roll+Mod mechanics rather than Roll Under. But at the end of the day a lot of these mechanical differences are a matter of give & take. Some mechanics work better for certain purposes but have set backs in other areas. One mechanic might be simpler or emphasize play speed, but may also lack specificity, or a bell curve, etc.

It depends on your preferences or what you want to emphasize in your system.

Yeah, opposed rolls are a bit more transparent with roll-over, that's true. But yes, roll-over and roll-under are such broad categories that I find specific implementations more valuable to examine in detail; to your point, it's about what one wants to emphasize for the game in question.

Quote from: zx81;1114424Yes, I know how to convert d20 to d100, but my question was about the probabilities for different outcomes in an roll-high-under-mechanic similar to BRP.
Theres got to be a chart listing the probabilities of different outcomes in the BRP opposed rolls system somewhere.

Assuming a tie goes to the defender:
Skills Attacker/Defender: 10/10  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/20  Probability miss/hit+parry/hit: 90.0/1.55/8.45
Skills Attacker/Defender: 10/30  Probability miss/hit+parry/hit: 90.0/2.55/7.45
Skills Attacker/Defender: 10/40  Probability miss/hit+parry/hit: 90.0/3.55/6.45
Skills Attacker/Defender: 10/50  Probability miss/hit+parry/hit: 90.0/4.55/5.45
Skills Attacker/Defender: 10/60  Probability miss/hit+parry/hit: 90.0/5.55/4.45
Skills Attacker/Defender: 10/70  Probability miss/hit+parry/hit: 90.0/6.55/3.45
Skills Attacker/Defender: 10/80  Probability miss/hit+parry/hit: 90.0/7.55/2.45
Skills Attacker/Defender: 10/90  Probability miss/hit+parry/hit: 90.0/8.55/1.45
Skills Attacker/Defender: 10/100  Probability miss/hit+parry/hit: 90.0/9.55/0.45
Skills Attacker/Defender: 20/10  Probability miss/hit+parry/hit: 80.0/0.55/19.45
Skills Attacker/Defender: 20/20  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/30  Probability miss/hit+parry/hit: 80.0/4.1/15.9
Skills Attacker/Defender: 20/40  Probability miss/hit+parry/hit: 80.0/6.1/13.9
Skills Attacker/Defender: 20/50  Probability miss/hit+parry/hit: 80.0/8.1/11.9
Skills Attacker/Defender: 20/60  Probability miss/hit+parry/hit: 80.0/10.1/9.9
Skills Attacker/Defender: 20/70  Probability miss/hit+parry/hit: 80.0/12.1/7.9
Skills Attacker/Defender: 20/80  Probability miss/hit+parry/hit: 80.0/14.1/5.9
Skills Attacker/Defender: 20/90  Probability miss/hit+parry/hit: 80.0/16.1/3.9
Skills Attacker/Defender: 20/100  Probability miss/hit+parry/hit: 80.0/18.1/1.9
Skills Attacker/Defender: 30/10  Probability miss/hit+parry/hit: 70.0/0.55/29.45
Skills Attacker/Defender: 30/20  Probability miss/hit+parry/hit: 70.0/2.1/27.9
Skills Attacker/Defender: 30/30  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/40  Probability miss/hit+parry/hit: 70.0/7.65/22.35
Skills Attacker/Defender: 30/50  Probability miss/hit+parry/hit: 70.0/10.65/19.35
Skills Attacker/Defender: 30/60  Probability miss/hit+parry/hit: 70.0/13.65/16.35
Skills Attacker/Defender: 30/70  Probability miss/hit+parry/hit: 70.0/16.65/13.35
Skills Attacker/Defender: 30/80  Probability miss/hit+parry/hit: 70.0/19.65/10.35
Skills Attacker/Defender: 30/90  Probability miss/hit+parry/hit: 70.0/22.65/7.35
Skills Attacker/Defender: 30/100  Probability miss/hit+parry/hit: 70.0/25.65/4.35
Skills Attacker/Defender: 40/10  Probability miss/hit+parry/hit: 60.0/0.55/39.45
Skills Attacker/Defender: 40/20  Probability miss/hit+parry/hit: 60.0/2.1/37.9
Skills Attacker/Defender: 40/30  Probability miss/hit+parry/hit: 60.0/4.65/35.35
Skills Attacker/Defender: 40/40  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 40/50  Probability miss/hit+parry/hit: 60.0/12.2/27.8
Skills Attacker/Defender: 40/60  Probability miss/hit+parry/hit: 60.0/16.2/23.8
Skills Attacker/Defender: 40/70  Probability miss/hit+parry/hit: 60.0/20.2/19.8
Skills Attacker/Defender: 40/80  Probability miss/hit+parry/hit: 60.0/24.2/15.8
Skills Attacker/Defender: 40/90  Probability miss/hit+parry/hit: 60.0/28.2/11.8
Skills Attacker/Defender: 40/100  Probability miss/hit+parry/hit: 60.0/32.2/7.8
Skills Attacker/Defender: 50/10  Probability miss/hit+parry/hit: 50.0/0.55/49.45
Skills Attacker/Defender: 50/20  Probability miss/hit+parry/hit: 50.0/2.1/47.9
Skills Attacker/Defender: 50/30  Probability miss/hit+parry/hit: 50.0/4.65/45.35
Skills Attacker/Defender: 50/40  Probability miss/hit+parry/hit: 50.0/8.2/41.8
Skills Attacker/Defender: 50/50  Probability miss/hit+parry/hit: 50.0/12.75/37.25
Skills Attacker/Defender: 50/60  Probability miss/hit+parry/hit: 50.0/17.75/32.25
Skills Attacker/Defender: 50/70  Probability miss/hit+parry/hit: 50.0/22.75/27.25
Skills Attacker/Defender: 50/80  Probability miss/hit+parry/hit: 50.0/27.75/22.25
Skills Attacker/Defender: 50/90  Probability miss/hit+parry/hit: 50.0/32.75/17.25
Skills Attacker/Defender: 50/100  Probability miss/hit+parry/hit: 50.0/37.75/12.25
Skills Attacker/Defender: 60/10  Probability miss/hit+parry/hit: 40.0/0.55/59.45
Skills Attacker/Defender: 60/20  Probability miss/hit+parry/hit: 40.0/2.1/57.9
Skills Attacker/Defender: 60/30  Probability miss/hit+parry/hit: 40.0/4.65/55.35
Skills Attacker/Defender: 60/40  Probability miss/hit+parry/hit: 40.0/8.2/51.8
Skills Attacker/Defender: 60/50  Probability miss/hit+parry/hit: 40.0/12.75/47.25
Skills Attacker/Defender: 60/60  Probability miss/hit+parry/hit: 40.0/18.3/41.7
Skills Attacker/Defender: 60/70  Probability miss/hit+parry/hit: 40.0/24.3/35.7
Skills Attacker/Defender: 60/80  Probability miss/hit+parry/hit: 40.0/30.3/29.7
Skills Attacker/Defender: 60/90  Probability miss/hit+parry/hit: 40.0/36.3/23.7
Skills Attacker/Defender: 60/100  Probability miss/hit+parry/hit: 40.0/42.3/17.7
Skills Attacker/Defender: 70/10  Probability miss/hit+parry/hit: 30.0/0.55/69.45
Skills Attacker/Defender: 70/20  Probability miss/hit+parry/hit: 30.0/2.1/67.9
Skills Attacker/Defender: 70/30  Probability miss/hit+parry/hit: 30.0/4.65/65.35
Skills Attacker/Defender: 70/40  Probability miss/hit+parry/hit: 30.0/8.2/61.8
Skills Attacker/Defender: 70/50  Probability miss/hit+parry/hit: 30.0/12.75/57.25
Skills Attacker/Defender: 70/60  Probability miss/hit+parry/hit: 30.0/18.3/51.7
Skills Attacker/Defender: 70/70  Probability miss/hit+parry/hit: 30.0/24.85/45.15
Skills Attacker/Defender: 70/80  Probability miss/hit+parry/hit: 30.0/31.85/38.15
Skills Attacker/Defender: 70/90  Probability miss/hit+parry/hit: 30.0/38.85/31.15
Skills Attacker/Defender: 70/100  Probability miss/hit+parry/hit: 30.0/45.85/24.15
Skills Attacker/Defender: 80/10  Probability miss/hit+parry/hit: 20.0/0.55/79.45
Skills Attacker/Defender: 80/20  Probability miss/hit+parry/hit: 20.0/2.1/77.9
Skills Attacker/Defender: 80/30  Probability miss/hit+parry/hit: 20.0/4.65/75.35
Skills Attacker/Defender: 80/40  Probability miss/hit+parry/hit: 20.0/8.2/71.8
Skills Attacker/Defender: 80/50  Probability miss/hit+parry/hit: 20.0/12.75/67.25
Skills Attacker/Defender: 80/60  Probability miss/hit+parry/hit: 20.0/18.3/61.7
Skills Attacker/Defender: 80/70  Probability miss/hit+parry/hit: 20.0/24.85/55.15
Skills Attacker/Defender: 80/80  Probability miss/hit+parry/hit: 20.0/32.4/47.6
Skills Attacker/Defender: 80/90  Probability miss/hit+parry/hit: 20.0/40.4/39.6
Skills Attacker/Defender: 80/100  Probability miss/hit+parry/hit: 20.0/48.4/31.6
Skills Attacker/Defender: 90/10  Probability miss/hit+parry/hit: 10.0/0.55/89.45
Skills Attacker/Defender: 90/20  Probability miss/hit+parry/hit: 10.0/2.1/87.9
Skills Attacker/Defender: 90/30  Probability miss/hit+parry/hit: 10.0/4.65/85.35
Skills Attacker/Defender: 90/40  Probability miss/hit+parry/hit: 10.0/8.2/81.8
Skills Attacker/Defender: 90/50  Probability miss/hit+parry/hit: 10.0/12.75/77.25
Skills Attacker/Defender: 90/60  Probability miss/hit+parry/hit: 10.0/18.3/71.7
Skills Attacker/Defender: 90/70  Probability miss/hit+parry/hit: 10.0/24.85/65.15
Skills Attacker/Defender: 90/80  Probability miss/hit+parry/hit: 10.0/32.4/57.6
Skills Attacker/Defender: 90/90  Probability miss/hit+parry/hit: 10.0/40.95/49.05
Skills Attacker/Defender: 90/100  Probability miss/hit+parry/hit: 10.0/49.95/40.05
Skills Attacker/Defender: 100/10  Probability miss/hit+parry/hit: 0.0/0.55/99.45
Skills Attacker/Defender: 100/20  Probability miss/hit+parry/hit: 0.0/2.1/97.9
Skills Attacker/Defender: 100/30  Probability miss/hit+parry/hit: 0.0/4.65/95.35
Skills Attacker/Defender: 100/40  Probability miss/hit+parry/hit: 0.0/8.2/91.8
Skills Attacker/Defender: 100/50  Probability miss/hit+parry/hit: 0.0/12.75/87.25
Skills Attacker/Defender: 100/60  Probability miss/hit+parry/hit: 0.0/18.3/81.7
Skills Attacker/Defender: 100/70  Probability miss/hit+parry/hit: 0.0/24.85/75.15
Skills Attacker/Defender: 100/80  Probability miss/hit+parry/hit: 0.0/32.4/67.6
Skills Attacker/Defender: 100/90  Probability miss/hit+parry/hit: 0.0/40.95/59.05
Skills Attacker/Defender: 100/100  Probability miss/hit+parry/hit: 0.0/50.5/49.5

If you want to make it simple and easy to grok, I suggest the following.

The TN to succeed is always 100.

You always roll d100 and add your relevant skill.  

If you succeed, your opponent can negate your success by rolling HIGHER.

Example:

If I have a 60% attack and my opponent has a 40% defend, and I roll a 90, my result is 150.  This is a success.  The opponent's BEST roll results in 140; they don't even need to roll since they can't negate my attack.

If I have a 40% attack and my opponent has a 60% defend and I roll a 45, my result is an 85.  This is a failure.  The opponent doesn't need to roll at all.  

If I have a 50% attack and my opponent has a 60% defend and I roll a 60, my total result is 110. This is a success.  My opponent may roll to negate my success.  They'd need a 51+ on their roll to negate my success.

Quote from: Pyromancer;1114432Assuming a tie goes to the defender:
Skills Attacker/Defender: 10/10  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/20  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/30  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/40  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/50  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/60  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/70  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/80  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/90  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 10/100  Probability miss/hit+parry/hit: 90.0/0.55/9.45
Skills Attacker/Defender: 20/10  Probability miss/hit+parry/hit: 80.0/1.55/18.45
Skills Attacker/Defender: 20/20  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/30  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/40  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/50  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/60  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/70  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/80  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/90  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 20/100  Probability miss/hit+parry/hit: 80.0/2.1/17.9
Skills Attacker/Defender: 30/10  Probability miss/hit+parry/hit: 70.0/2.55/27.45
Skills Attacker/Defender: 30/20  Probability miss/hit+parry/hit: 70.0/4.1/25.9
Skills Attacker/Defender: 30/30  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/40  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/50  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/60  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/70  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/80  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/90  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 30/100  Probability miss/hit+parry/hit: 70.0/4.65/25.35
Skills Attacker/Defender: 40/10  Probability miss/hit+parry/hit: 60.0/3.55/36.45
Skills Attacker/Defender: 40/20  Probability miss/hit+parry/hit: 60.0/6.1/33.9
Skills Attacker/Defender: 40/30  Probability miss/hit+parry/hit: 60.0/7.65/32.35
Skills Attacker/Defender: 40/40  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 40/50  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 40/60  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 40/70  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 40/80  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 40/90  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 40/100  Probability miss/hit+parry/hit: 60.0/8.2/31.8
Skills Attacker/Defender: 50/10  Probability miss/hit+parry/hit: 50.0/4.55/45.45
Skills Attacker/Defender: 50/20  Probability miss/hit+parry/hit: 50.0/8.1/41.9
Skills Attacker/Defender: 50/30  Probability miss/hit+parry/hit: 50.0/10.65/39.35
Skills Attacker/Defender: 50/40  Probability miss/hit+parry/hit: 50.0/12.2/37.8
Skills Attacker/Defender: 50/50  Probability miss/hit+parry/hit: 50.0/12.75/37.25
Skills Attacker/Defender: 50/60  Probability miss/hit+parry/hit: 50.0/12.75/37.25
Skills Attacker/Defender: 50/70  Probability miss/hit+parry/hit: 50.0/12.75/37.25
Skills Attacker/Defender: 50/80  Probability miss/hit+parry/hit: 50.0/12.75/37.25
Skills Attacker/Defender: 50/90  Probability miss/hit+parry/hit: 50.0/12.75/37.25
Skills Attacker/Defender: 50/100  Probability miss/hit+parry/hit: 50.0/12.75/37.25
Skills Attacker/Defender: 60/10  Probability miss/hit+parry/hit: 40.0/5.55/54.45
Skills Attacker/Defender: 60/20  Probability miss/hit+parry/hit: 40.0/10.1/49.9
Skills Attacker/Defender: 60/30  Probability miss/hit+parry/hit: 40.0/13.65/46.35
Skills Attacker/Defender: 60/40  Probability miss/hit+parry/hit: 40.0/16.2/43.8
Skills Attacker/Defender: 60/50  Probability miss/hit+parry/hit: 40.0/17.75/42.25
Skills Attacker/Defender: 60/60  Probability miss/hit+parry/hit: 40.0/18.3/41.7
Skills Attacker/Defender: 60/70  Probability miss/hit+parry/hit: 40.0/18.3/41.7
Skills Attacker/Defender: 60/80  Probability miss/hit+parry/hit: 40.0/18.3/41.7
Skills Attacker/Defender: 60/90  Probability miss/hit+parry/hit: 40.0/18.3/41.7
Skills Attacker/Defender: 60/100  Probability miss/hit+parry/hit: 40.0/18.3/41.7
Skills Attacker/Defender: 70/10  Probability miss/hit+parry/hit: 30.0/6.55/63.45
Skills Attacker/Defender: 70/20  Probability miss/hit+parry/hit: 30.0/12.1/57.9
Skills Attacker/Defender: 70/30  Probability miss/hit+parry/hit: 30.0/16.65/53.35
Skills Attacker/Defender: 70/40  Probability miss/hit+parry/hit: 30.0/20.2/49.8
Skills Attacker/Defender: 70/50  Probability miss/hit+parry/hit: 30.0/22.75/47.25
Skills Attacker/Defender: 70/60  Probability miss/hit+parry/hit: 30.0/24.3/45.7
Skills Attacker/Defender: 70/70  Probability miss/hit+parry/hit: 30.0/24.85/45.15
Skills Attacker/Defender: 70/80  Probability miss/hit+parry/hit: 30.0/24.85/45.15
Skills Attacker/Defender: 70/90  Probability miss/hit+parry/hit: 30.0/24.85/45.15
Skills Attacker/Defender: 70/100  Probability miss/hit+parry/hit: 30.0/24.85/45.15
Skills Attacker/Defender: 80/10  Probability miss/hit+parry/hit: 20.0/7.55/72.45
Skills Attacker/Defender: 80/20  Probability miss/hit+parry/hit: 20.0/14.1/65.9
Skills Attacker/Defender: 80/30  Probability miss/hit+parry/hit: 20.0/19.65/60.35
Skills Attacker/Defender: 80/40  Probability miss/hit+parry/hit: 20.0/24.2/55.8
Skills Attacker/Defender: 80/50  Probability miss/hit+parry/hit: 20.0/27.75/52.25
Skills Attacker/Defender: 80/60  Probability miss/hit+parry/hit: 20.0/30.3/49.7
Skills Attacker/Defender: 80/70  Probability miss/hit+parry/hit: 20.0/31.85/48.15
Skills Attacker/Defender: 80/80  Probability miss/hit+parry/hit: 20.0/32.4/47.6
Skills Attacker/Defender: 80/90  Probability miss/hit+parry/hit: 20.0/32.4/47.6
Skills Attacker/Defender: 80/100  Probability miss/hit+parry/hit: 20.0/32.4/47.6
Skills Attacker/Defender: 90/10  Probability miss/hit+parry/hit: 10.0/8.55/81.45
Skills Attacker/Defender: 90/20  Probability miss/hit+parry/hit: 10.0/16.1/73.9
Skills Attacker/Defender: 90/30  Probability miss/hit+parry/hit: 10.0/22.65/67.35
Skills Attacker/Defender: 90/40  Probability miss/hit+parry/hit: 10.0/28.2/61.8
Skills Attacker/Defender: 90/50  Probability miss/hit+parry/hit: 10.0/32.75/57.25
Skills Attacker/Defender: 90/60  Probability miss/hit+parry/hit: 10.0/36.3/53.7
Skills Attacker/Defender: 90/70  Probability miss/hit+parry/hit: 10.0/38.85/51.15
Skills Attacker/Defender: 90/80  Probability miss/hit+parry/hit: 10.0/40.4/49.6
Skills Attacker/Defender: 90/90  Probability miss/hit+parry/hit: 10.0/40.95/49.05
Skills Attacker/Defender: 90/100  Probability miss/hit+parry/hit: 10.0/40.95/49.05
Skills Attacker/Defender: 100/10  Probability miss/hit+parry/hit: 0.0/9.55/90.45
Skills Attacker/Defender: 100/20  Probability miss/hit+parry/hit: 0.0/18.1/81.9
Skills Attacker/Defender: 100/30  Probability miss/hit+parry/hit: 0.0/25.65/74.35
Skills Attacker/Defender: 100/40  Probability miss/hit+parry/hit: 0.0/32.2/67.8
Skills Attacker/Defender: 100/50  Probability miss/hit+parry/hit: 0.0/37.75/62.25
Skills Attacker/Defender: 100/60  Probability miss/hit+parry/hit: 0.0/42.3/57.7
Skills Attacker/Defender: 100/70  Probability miss/hit+parry/hit: 0.0/45.85/54.15
Skills Attacker/Defender: 100/80  Probability miss/hit+parry/hit: 0.0/48.4/51.6
Skills Attacker/Defender: 100/90  Probability miss/hit+parry/hit: 0.0/49.95/50.05
Skills Attacker/Defender: 100/100  Probability miss/hit+parry/hit: 0.0/50.5/49.5

Thanks!
Last night I calculated D20 14/10 and 10/14 (Attacker/Defender, equal to D100 70/50 and 50/70), and got this (your D100 numbers below) :
Roll high under, ties goes to defender
14/10 Probability miss/hit+parry/hit: 30.0/13.75/56.25
70/50 Probability miss/hit+parry/hit: 30.0/22.75/47.25

10/14 Probability miss/hit+parry/hit: 50.0/23.75/26.25
50/70 Probability miss/hit+parry/hit: 50.0/12.75/37.25

I also did roll low under - lowest succesful roll wins:
14/10 Probability miss/hit+parry/hit: 30.0/23.75/46.25
10/14 Probability miss/hit+parry/hit: 50.0/13.75/36.25

Due to a sick kid, I haven´t slept more than a few hours a night the last week, so this might well be wrong.
Assuming my numbers are correct, the difference between D20 and D100 seems bigger than I would expect.

Quote from: zx81;1114540Thanks!
Last night I calculated D20 14/10 and 10/14 (Attacker/Defender, equal to D100 70/50 and 50/70), and got this (your D100 numbers below) :
Roll high under, ties goes to defender
14/10 Probability miss/hit+parry/hit: 30.0/13.75/56.25
70/50 Probability miss/hit+parry/hit: 30.0/22.75/47.25

10/14 Probability miss/hit+parry/hit: 50.0/23.75/26.25
50/70 Probability miss/hit+parry/hit: 50.0/12.75/37.25

I also did roll low under - lowest succesful roll wins:
14/10 Probability miss/hit+parry/hit: 30.0/23.75/46.25
10/14 Probability miss/hit+parry/hit: 50.0/13.75/36.25

Due to a sick kid, I haven´t slept more than a few hours a night the last week, so this might well be wrong.
Assuming my numbers are correct, the difference between D20 and D100 seems bigger than I would expect.

There was an error in my calculation, I corrected the numbers in my earlier post. The slight difference between the D100 and D20 numbers are caused by the higher probability of a tie with the D20.

Quote from: Pyromancer;1114544There was an error in my calculation, I corrected the numbers in my earlier post. The slight difference between the D100 and D20 numbers are caused by the higher probability of a tie with the D20.

That makes sense (I had already copied and printed the wrong numbers, and cut/pasted from the saved file).
I´ll have to stay awake again tonight for sure, so I´ll compare this with my current houserules and see if it looks any better.
Thank you again, this was very helpful!
Thanks also to everyone else, especially for putting up with my poor english. I could have got this answer at a swedish site (I think there is still one active), but THERPGSITE is one of the few places left on the internet, where everyone is not compleatly retarded.
I´ll read the whole thread when I´ve got more time.

EDIT: Ok, apparently that might be read like I´m calling everyone on that swedish site a retard. Dont read it like that.

Quote from: Razor 007;1114295I understand the mechanic you describe; but if the goal is to roll equal to or under, I think lower should always be better.

There, now the world is a better place...

Roll High Under is a lot like blackjack (or Cribbage, or The Price is Right), you want to get as high a roll as possible without going over.

I think that's better than roll low, actually. People are wired to think a higher number is better than a lower one, while "going too far" is also a concept easy to process.