The negative binomial distribution is a kind of discrete probability distribution in statistics, which is also called PASCAL or polier distribution. For the analysis of counting data, with the probability of integer values from 0 to infinity. The negative binomial distribution is similar to Bernoulli’s test. But unlike the Bernoulli test, which indicates the number of successes, the negative binomial indicates the number of failures that occur at the beginning of the sequence until a given number of successes are achieved; It’s different from the poisson distribution where the allowable conditions are greater than the mean of the conditions. The negative binomial distribution is a process.
Negative binomial distribution formula:
Negative binomial distribution P(X = r) = n-1 cr -1 pr (1- P)n-r
So this combination n minus 1 cr minus 1 is equal to ((n minus 1) factorial. / (n – 1) – (r – 1)). )/(r – 1)!