Probability curve for TW2013

[Michael Lewis]

"The rule set in 2013 is something I really want to like. But the more I look at it, and try to handle the parts I don't like (mainly the odds of getting certain results), I'm looking at a complete rewrite. But depending what type of game you want to run, those probability curves can work in your favor, as people not aware of it most likely will think they have a very different odds of success than they really have (on 3D20L, you have 14% chance of scoring a '1', almost 50% to get '4' or less, and 90% to get 11 or less).

Edit: Perhaps I should add that my "problem" with 2013 is the combination of the probability curve, the curve ends at '1', and the positive bonuses are tied to the number of dices. Making it open ended downwards, and rebalance it, would probably do the trick for me. If the game is "competent characters surviving 'against the odds'", I think it will fit right in (5D20L gives slightly over 20% to score that impossible '1', 40% to score a '2' or better, and 55% to score a '3' or better, the 90% mark is around '7' or '8')."

This was quoted from Lundgren from a previous post.

Has anyone who's played TW2013 had problems with such high probabilities?
I've played around just rolling 3d20 L and found it very difficult to fail most of the time.

Michael

[stg58fal]

3D20 is "Professional". So IMO, in a vacuum they SHOULD succeed a significant % of the time.

That's what penalties for improvised tools, poor lighting, -30 degree temperatures with snow driven by a 40 mph wind, wounds, etc., are for.

Also just because you're mathematically SUPPOSED to succeed X number of times in Y tries with Z odds doesn't mean you WILL. I've seen far too many times in gaming where someone needed to roll a 5 or better on D20, and what do they get? A 2. Heck, it's happened to me. "As long as I don't roll a 1, this guys is toast". *rolls die* "A ONE?!?!!?! YOU GOTTA BE SHITTIN ME!!!1111!!!!"

It's happened to me GMing T2013. Russians trying to shoot my players, I'm rolling three dice for this particular group of baddies, with modifiers I need something like a 12 or less to hit. Dice come up 17, 19, 20. Or anything else greater than 12. Every. Single. Time.

Dice are one of the VERY few things where I place pretty much no faith in probability. Every outcome is as probable as every other outcome...in theory. Reality, though, is a whole different bird.

[ZombieLenin]

You know, this probably does not pass copyright muster for re-distribution, but I've been thinking over the last week about just this--how the reflex system obfuscates prectile chance of success.

As a result, I've been wishing that there was a conversion out there of the Reflex system to straight percentile. Then it occurred to me that this could be converted to Fantasy Flight's Warhammer 40k RPG: Only War.

That particular game has these things going for it:
1. Percetile system, with hitlocation built in
2. Detailed weapons that already take into account ammunition
3. Built in rules for PCs controlling NPC "squad mates"
4. Related to 1, a very brutal combat system, complete with critical hit tables, that mimics the lethality of T2000 and TW2013 (if you drop fate points)
5. An insanity sytem that is used to model the horrors of war/combat/ptsd specifically (as well as the other mind breaking elements of 40k)
6. Rules for vehicle combat

If someone who had a bit more knowledge about modern military weapons and vehicles were to port them over to Only War (dropping out all of the "magical" elements of 40k), I think you'd have a great--transparent--system for running games in T2000/T2013 settings.

In fact, if we weren't looking to run a game (partially) for a journalistic review, I'd seriously think about accepting the Warhammer weapons and vehicle rules and just reskin them. I'd literally call just use the stats for Warhammer "slugthrower" assault rifles for all real world assault rifles, etc; However, I imagine that would ruin some of the fun for a lot of T2000/T2013 fans.

[kato13]

(Long and math focused post, sorry)


I have never thought that a d20 was sufficiently random for gaming situations. A 5% chance for perfection and a 5% chance for total failure always seemed too high for me.

I use d100 but process it into the equivalent of a d19(?). Usually you can substitute this for a d20 roll. If low is good you leave it as is and make 19 a disaster. If high is good you add 1 and make 2 the disaster roll.

I'll explain.

When I was first gaming I discovered 1+2+3+4+5+6+7+8+9+10+9+8+7+6+5+4+3+2+1 = 100

That led me to create the following chart

 d100 |     d19
----------------
   1          1
  2-3         2
  4-6         3
  7-10        4
 11-15        5
 16-21        6
 22-28        7
 29-36        8
 37-45        9
 46-55       10
 56-64       11
 65-72       12
 73-79       13
 80-85       14
 86-90       15
 91-94       16
 95-97       17
 98-99       18
  100        19

Ok here is a graph of how the probability curve you mentioned works with d20s



As you mentioned the chances of a low roll present themselves as being hugely common once you get into multiple dice.

If you switch to my d19 system the chance for a very low roll increases much more gradually.


For example with 5 sets of dice the chance of getting a 4 as the lowest roll is 67.23% using d20 but only 40% using my d19 system.

It might be more math that some people want but if find it shifts the probability nicely.

[Lundgren]

Originally Posted by stg58fal

3D20 is "Professional". So IMO, in a vacuum they SHOULD succeed a significant % of the time.

That's what penalties for improvised tools, poor lighting, -30 degree temperatures with snow driven by a 40 mph wind, wounds, etc., are for.

I have no problem with a professional being a lot beter than an untrained amateur. kato13's graphs shows exactly what I mean. There is quite a gap between the hardest possible and completely impossible when skilled.

The second graph is more what I would want. But using a D100 and then get another value from a table would lose the elegance of the 3D20L check. I have a big pile of Phoenix Command and orher Leading Edge books if I want to go that route A few pre-calculations and it can be a quite fast playing system.

I have been toying with a quick and dirty idea of using a D6 to create an open ended scale without gaps. The twenty sided dices would still handle the results between two and twenty. But if I go down that road, I guess I would get an itch to change the modifiers, etc, as well to take that change into account.

[kato13]

Originally Posted by Lundgren

The second graph is more what I would want. But using a D100 and then get another value from a table would lose the elegance of the 3D20L check. I have a big pile of Phoenix Command and orher Leading Edge books if I want to go that route A few pre-calculations and it can be a quite fast playing system.

Yeah my system will never catch on and it does not work the best here (it works best on incremental success rather than pass/fail).

Originally Posted by Lundgren

I have been toying with a quick and dirty idea of using a D6 to create an open ended scale without gaps. The twenty sided dices would still handle the results between two and twenty. But if I go down that road, I guess I would get an itch to change the modifiers, etc, as well to take that change into account.

If you finalize anything and want to see the curves let me know. I've been trying to solve this over the past few days and have not found an elegant solution yet.

[Lundgren]

Originally Posted by kato13

Yeah my system will never catch on and it does not work the best here (it works best on incremental success rather than pass/fail).

Depends. If all the relevant charts can be printed on one A4/letter size paper, something like that can be fast and useful.

If you finalize anything and want to see the curves let me know. I've been trying to solve this over the past few days and have not found an elegant solution yet.

Then I can't help you. I said "quick and dirty"

But I think the mechanic is simple enough. If getting a 1, roll a D6. Keep on rolling the D6 until it doesn't end up as a one. First D6 is -5 + D6, second is -10 + D6, third is -15 + D6, and so on.

Getting a 6 will go back to the 1 of the former dice, closing the gap some open ended roll system tend to have. The D6 also gives the advantage of ending up on an incremental of fives, making the math during play a bit easier.

The odds of a 3D20L, with this addon, to get a -6 is about 1,6%, while that untrained shooter with 2D20H as a 0,03% chance.

[kato13]

Originally Posted by Lundgren

Depends. If all the relevant charts can be printed on one A4/letter size paper, something like that can be fast and useful.

Then I can't help you. I said "quick and dirty"

But I think the mechanic is simple enough. If getting a 1, roll a D6. Keep on rolling the D6 until it doesn't end up as a one. First D6 is -5 + D6, second is -10 + D6, third is -15 + D6, and so on.

Getting a 6 will go back to the 1 of the former dice, closing the gap some open ended roll system tend to have. The D6 also gives the advantage of ending up on an incremental of fives, making the math during play a bit easier.

The odds of a 3D20L, with this addon, to get a -6 is about 1,6%, while that untrained shooter with 2D20H as a 0,03% chance.

I like it. However I have a few questions. If a 5d20 produces 2 or more 1 would you get 2 or more chances on the d6 tree. I did not think your graph presented that, but was not sure.

I was also thinking of using different dice like a d12 for 5d20, a d10 for 4d20, a d8 for 3 d20, etc.

If we consider sub 1 results to be unusually superior, I like what the graph shows

[Lundgren]

Originally Posted by kato13

I like it. However I have a few questions. If a 5d20 produces 2 or more 1 would you get 2 or more chances on the d6 tree. I did not think your graph presented that, but was not sure.

Just one D6, regardless of the number of 1's turning up. When I considered using on D6 per '1', I realized the "dent" in the line would be even worse.

I was also thinking of using different dice like a d12 for 5d20, a d10 for 4d20, a d8 for 3 d20, etc.

My main concern with different dice sizes is the lag in remembering what dice to use, and the math to get the final result. If it is people used to juggle numbers, I don't think it would matter much. But I think it might affect the speed for quite a few.

My design parameter in this case is however "the fastest system of those that are good enough for me." Change those words just a little, or have another threshold of "good enough", and the D6 solution might not cut it anymore.

[kato13]

Originally Posted by Lundgren

My design parameter in this case is however "the fastest system of those that are good enough for me." Change those words just a little, or have another threshold of "good enough", and the D6 solution might not cut it anymore.

I find more often than not that I ignore the old adage that "The perfect is the enemy of the good", during my initial analysis. I try to step back a bit in the end.

[Lundgren]

Originally Posted by kato13

I find more often than not that I ignore the old adage that "The perfect is the enemy of the good", during my initial analysis. I try to step back a bit in the end.

I think "perfect is the enemy of getting it to completion" would be more true

But it also remind me what some database programmer apparently once said "I can make it fast, reliable, and cheap. Pick two."

I guess the equivalent for roleplaying systems are "Fast, detailed, and easy to understand. Pick two."