Chaosforge Forum

General => Off Topic => Topic started by: ZicherCZ on September 20, 2013, 05:21

Title: Online dice probability calculator
Post by: ZicherCZ on September 20, 2013, 05:21
Now there's something I've been trying to find for quite some time - a calculator to which you can input a dice notation and the calculator will display the chance of the roll being higher or lower than a certain result.
For example, what's the chance of killing a demon with one BFG shot?
Now we know that a BFG is 10d6 damage, demon has 2 armor and 25 HP, so what's the probability of 10d6 >= 27?

I found the calculator here at anydice.com (http://anydice.com/). I thought about sharing this with the rest of us here.

By the way, the probability of the example is over 94% :).
Title: Re: Online dice probability calculator
Post by: thelaptop on September 20, 2013, 07:59
Um.  By Law of Large Numbers, as the number of dice and sides go up (xdy), the distribution tends towards a normal distribution with μ = xE[dy] ~ x (1+y)/2, and σ² = Var[xdy], with an abuse of notation.

So your question can be recast into a "simple" look up on the normal distribution.

>.<

But the site is still cool.  Heheheheh...
Title: Re: Online dice probability calculator
Post by: slave on September 20, 2013, 08:28
I have used Wolfram Alpha (http://www.wolframalpha.com/input/?i=3d5%3E10&a=*MC.d5-_*DiceNotation-&a=UnitClash_*d.*Days.dflt--) for calculating these probabilities. The site you used is better for that purpose though.

Quote
For example, what's the chance of killing a demon with one BFG shot?
Now we know that a BFG is 10d6 damage, demon has 2 armor and 25 HP, so what's the probability of 10d6 >= 27?

Also, you probably know that, but the BFG deals plasma damage, which means that you should calculate the probability for 10d6 >= 26, since the effect of armor is halved.
Title: Re: Online dice probability calculator
Post by: emulord on September 20, 2013, 12:34
This could be VERY useful for determining how many levels of Brute to take before taking other skills in a Angel of Berzerk run
Title: Re: Online dice probability calculator
Post by: ZicherCZ on September 21, 2013, 02:00
Thelaptop, that was a sample question. In fact, my motivation to find a site like this dates back to the time when WIKICOMP was still active. Plus, I was not asking for an average nor standard deviation ;).

Also, you probably know that, but the BFG deals plasma damage, which means that you should calculate the probability for 10d6 >= 26, since the effect of armor is halved.
Oops, you caught me here. Even as a sample question, it should have been a correct question.
Title: Re: Online dice probability calculator
Post by: ParaSait on September 21, 2013, 08:21
Um.  By Law of Large Numbers, as the number of dice and sides go up (xdy), the distribution tends towards a normal distribution with μ = xE[dy] ~ x (1+y)/2, and σ² = Var[xdy], with an abuse of notation.

So your question can be recast into a "simple" look up on the normal distribution.

>.<

But the site is still cool.  Heheheheh...
Maybe one could keep that method for in case someone is looking. Then one can show off what a cool math geek he is. :P