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20111004, 03:52 PM (ISO 8601)
 Join Date
 Mar 2011
Math and Game Effects of Bell Curve variant d20? [3.x]
So lacking the mathematical skills to do the analysis myself (or rather the time to learn the equations and run them) I was wondering how much "Bell Curve" alternate rules (Specifically 3d6, but if there are others, I'm open to them) change the basic assumptions of the d20 system, particularly 3.5 and PF.
Without any calculations, it seems like it makes BAB and AC variance between equal level opponents far more important. When most of the rolls end up between 9 and 12, that extra point that takes you out of the range would make far more than a 5% difference.
Similar logic would apply to skills. Skill ranks and taking 10 would be far more powerful than just hoping for a lucky roll. This makes sense to me from a "realism" standpoint, why can an adventurer who's lucky make a better suit of armor than a smith who has put in decades of practice to learn the art and takes the extra time to be sure it's made just right?
I'm still assembling what will probably be an E6 or E10 homebrew, and given those parameters, would the bell curve distribution have different effects?
I know from a statistical standpoint 3d6 is a pretty bad curve, but anyone with Yahtzee or Shadowrun will have enough. Would, say, 5d4 be better? I know that altering critical threat ranges and such would be a pain, whereas at least 3d6 has already set modifications. How about percentile dice with a gaussian curve in table format?

20111004, 04:14 PM (ISO 8601)
 Join Date
 Nov 2010
 Location
 Beyond the Ninth Wave
 Gender
Re: Math and Game Effects of Bell Curve variant d20? [3.x]
While you're correct on skill ranks being more valuable, things like taking 10 are dramatically less valuable because everyone rolls 10 all the time anyway. Taking 20 (18, I guess), on the other hand, is very much worth it.
As for alternate rolling systems in general: The more dice you add, the more predictable a roll is going to be. One die, on the other hand, will behave strangely on a consistent basis. 3d6 is elegant in that it's predictable and its average (10.5) is that same as that of a d20. Likewise for 2d10 (though that's somewhat more erratic).
5d4 would result in noticeably higher rolls, with an average of 12.5, and would be even more predictable than 3d6, with rolls hitting 1213 an overwhelming amount of the time.Last edited by gkathellar; 20111004 at 04:14 PM.
Originally Posted by KKL

20111004, 04:33 PM (ISO 8601)
 Join Date
 Sep 2009
Re: Math and Game Effects of Bell Curve variant d20? [3.x]
Basically, although it makes things even less relevant when attack rolls tend to be well over AC.
I'm still assembling what will probably be an E6 or E10 homebrew, and given those parameters, would the bell curve distribution have different effects?
I know from a statistical standpoint 3d6 is a pretty bad curve
Would, say, 5d4 be better?
If you want the same average and roughly the same effective spread as 1d20, but with a bell curve, 11d628 gives a very good approximation to the bell curve.
I know that altering critical threat ranges and such would be a pain, whereas at least 3d6 has already set modifications. How about percentile dice with a gaussian curve in table format?