Chance of success after multiple attempts.

Kasseo

New member
Ok, so, this has probably been asked about 50 times, but I just can't find it, because I don't really know how to phrase the problem properly for the search engine.

So, following:

Chance of event occurring is 2% (aka a 50 sided die rolling a natural 1). How to calculate the probability of the event occurring once after multiple attempts? So let's say I roll 10d50, meaning it's 10 times a 2% chance. The only thing I remember from school is that it's not 20%, since that would lead to 100% at 50d50, which in term is Gambler's Fallacy and not actual math XD

Thanks for the help in advance.

Kasseo

New member
Yeah...no clue how the heck to even read that formula, but I've found a calculator by looking for Binomial Distribution. Thanks^^

tkhunny

Moderator
Staff member
I'm thinking you'll have better success with the Negative Binomial. It's more of a Survival Function.

p = probability of success
q = 1-p

p(1st roll) = p
p(2nd roll) = q*p
p(3rd roll) = q*q*p = q^2 * p
...
p(50th roll) = q^49 * p
...
etc.