NBINOM - negative binomial distribution

The negative binomial distribution models the toss of a manipulated coin that does not have the same chance for heads and tails until a specified number of heads is reached. The variable of a negative binomial distribution has non-negative integer values and its value is the count of tails.

The negative binomial distribution has two parameters, the number of successes that are required to stop the series of Bernoulli trials, and the probability of success.