This is a binomial probability calculator. Given that a single Bernoulli trial has a success probability of p, it tells you the probability of getting k successes out of n trials.
For example, it can tell you the probabilities of these events:
The probability of exactly k successes from n trials, where each trial has a success probability of 0 ≤ p ≤ 1, is given by the formula:
P(X = k) = nCr(n, k)pk(1−p)n−k
where the combination function nCr(n, k) is given by:
nCr(n, k) =n!k!(n − k)!
The cumulative probabilities of obtaining at most or at least x successes is then obtained by summing the probabilities for 0 ≤ k ≤ x and for x ≤ k ≤ n respectively.
This tool uses a special kind of floating-point number class with a large exponent range. This means it can calculate very low probabilities but only to the same level of precision as an ordinary 64-bit float. The tool shows you 10 digits.
“isn't complete crap”