05262015, 01:37 AM  #1 
GURPS FAQ Keeper
Join Date: Mar 2006
Location: Kyïv, Ukraine

Formulae for calculating Storyteller / Exalted d10 probabilities?
Greetings, all!
I've searched the web, and I can't find a transparent calculation of probabilities for Storytellerderived Exalted dice pool successes. The results I've found seem inconsistent, and I don't think I can figure which ones are more correct. I've considered writing a bruteforce calculation, but this isn't a good idea, as dice pools can easily go all the way past 20×d10. The basic rules of dice are as follows: Each d10 is rolled once. A result of 7,8,9 adds one success to the roll, while a result of 10 on the die adds two successes. There are no rerolls, and no subtractions. How do I calculate the probability of each number of successes for a given dice pool? Thanks in advance! 
05262015, 01:45 AM  #2 
Join Date: Feb 2005
Location: Berkeley, CA

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
http://anydice.com/program/5e8a (that's for 5d, but should be easy to adjust)

05262015, 03:17 AM  #3  
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Join Date: Mar 2006
Location: Kyïv, Ukraine

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
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05262015, 03:32 AM  #4 
Join Date: Jul 2007

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
Not sure this is what you want, but this has tables, I don't know if it covers Exalted:
The distribution of World of Darkness dice rolls Ralf H¨uls (huels@amadeus.statistik.unidortmund.de) August 21, 1996 http://www.scribd.com/doc/46230301/d...ability#scribd 
05262015, 12:22 PM  #5 
Join Date: Feb 2005
Location: Berkeley, CA

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
By the time it's any large number of dice you've got a curve that's essentially indistinguishable from a normal curve with mean = 0.5 * dice and std deviation = sqrt(0.45*dice). However, Anydice with my setup seems fine at 100d, which should be more than you ever need.

05262015, 12:28 PM  #6  
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Join Date: Mar 2006
Location: Kyïv, Ukraine

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
Quote:
I did find StDev, but couldn't meaningfully convert it to actual probabilities of X successes. And I wonder why your setup is so much faster than counting 7's10's on dice. It feels as if the 7scounting op is extremely inefficient. 

05262015, 01:06 PM  #7 
Join Date: Jun 2005
Location: Lawrence, KS

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
I did that many years ago on Excel, getting exact odds for every outcome. But it was a rather complicated iterative algorithm to implement. It would be a lot of work to set up and I'm not sure I could verbalize it.
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05262015, 05:40 PM  #8 
Hero of Democracy
Join Date: Mar 2012
Location: far from the ocean

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
Vicky, you can program, right?
Code:
var single = []; single[0]=.6; single[1]=.3; single[2]=.1; function combine(a,b){var result=[]; for(var i=0;i<a.length;i++)for(var j=0;j<b.length;j++){var x = i+j; if(!result[x])result[x]=0; result[x]+=a[i]*b[j];} return result;} var pool = function (x){var result = single; for(var i=1;i<x;i++) result = combine(result,single); return result;} The algorithm is fast, relying on probability rather than brute force.
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05262015, 06:39 PM  #9  
Join Date: Feb 2005
Location: Berkeley, CA

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
Quote:
Spreadsheet version: https://docs.google.com/spreadsheets...it?usp=sharing Last edited by Anthony; 05262015 at 06:53 PM. 

05272015, 01:43 AM  #10  
GURPS FAQ Keeper
Join Date: Mar 2006
Location: Kyïv, Ukraine

Re: Formulae for calculating Storyteller / Exalted d10 probabilities?
To a certain extent. I'm at least half selftaught, and working in a somewhat peculiar narrow subset of C#, so might not know some things. Still, Java seems readable, being of a related family or something.
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Tags 
dice, dice pool, exalted, probability, storyteller, theorycraft 
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