View Full Version : Help with dice averages.

Dragonus45

2013-03-01, 07:38 AM

Me and my brother are working on a game system with d6s where a pool is rolled and 5-6 are succeses. But were hitting a stump trying to work out averages, i can work them out a little, but he is just hopeless. Does anyone know if there is a tool out there or a tutorial for working out averages like that?

:EDIT: I can find stuff for normal avarages, but averages for rolls of 5-6 or rolls of 5-6 with how often a 1 might come up along the rest of that and all that are a bit beyond me.

Fortuna

2013-03-01, 07:57 AM

Try http://anydice.com/

Depending on what you mean by 'average', a little programming will get your problem done for you. If you have any more specific problems I can see what I can cobble together.

EDIT: Rolling a pool of each size from one to ten, counting fives and sixes (http://anydice.com/program/1e96) and the same, counting ones (http://anydice.com/program/1e97) sound like what you wanted. The Summary tab provides the mean (i.e. the average count). The At Least tab will tell you the probability of getting at least a given number (obviously).

Dragonus45

2013-03-01, 08:07 AM

Thanks, i had actually found that but i couldn't program it to make it do what i wanted.

Jack of Spades

2013-03-01, 08:07 AM

Not sure what you mean by average, but I'll try to be useful...

Chance of a given number being rolled on a single d6 is ~18.89% or 1/6.

Chance or a 5 or a 6 is therefore ~33.33% or 1/3.

So, an average (not to be confused with typical) roll of [n]d6 will yield n/6 1's and n/3 5's or 6's.

So, figure out what the human average is for a given dice pool in your game (I'll call that x). A "typical" (mildly challenging, but not too tough) challenge should probably have a target number of successes equal to x/3. If 1's cancel out successes, then it should be x/3-x/6=x/6. Anything less than that should be considered easy, anything more should be exceptionally tough.

Or I'm just completely wrong about all of this. I like to keep that option open.

Rhynn

2013-03-01, 09:43 AM

Not sure what you're trying to work out, exactly. Is it the chance to get any X successes (5-6 on d6) when rolling any N d6s?

That's your basic binomial distribution (http://en.wikipedia.org/wiki/Binomial_distribution) where p = 0.5, n is the number of dice rolled, and i is the number of successes you're calculating the probability for.

Easiest thing to do is to plug this into Excel / OpenOffice Calc:

=(COMBIN(n;i))*(POWER(p;i))*(POWER(1-p;n-i))

You can make a table of it, with n and i values on the rows and columns (or the other way around), if you know Excel / Calc spreadsheet basics.

Plugging that in, for instance, I can see that, rolling 6 dice, the chance of 0 successes is 8.8%, 1 success is 26.3%, 2 successes is 32.9%, 3 successes is 22.0%, 4 successes is 8.2%, 5 successes is 1.7%, and 6 successes is 0.1%.

NB: If my math is wrong, somebody spank me over it. Haven't done binomial distribution in a while.

Jay R

2013-03-01, 10:27 AM

If you will ask a specific question, we'll answer it, but we need to know the question.

What, exactly, do you want to calculate?

Andreaz

2013-03-01, 10:41 AM

Thanks, i had actually found that but i couldn't program it to make it do what i wanted.Make custom dice. If your d6 rolls "1 success on a 5 or 6" and "-1 success on a 1", you want a die that looks like this: {-1,0,0,0,1,1}

It ends more or less like this: http://anydice.com/program/1e98

Dragonus45

2013-03-01, 12:25 PM

If you will ask a specific question, we'll answer it, but we need to know the question.

What, exactly, do you want to calculate?

Some random guy gave me what i really needed, and andreaz put up the other thing that was icing, from here i guess i can manage whatever i need with a little playing around with the anydice thing.

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