PHP Manual: Probability mass function of the negative binomial distribution

Description

float stats_dens_pmf_negative_binomial(float $x, float $n, float $pi)

Returns the probability mass at x, where the random variable follows the negative binomial distribution of which the number of the success is n and the success rate is pi.

Parameters

x: The value at which the probability mass is calculated
n: The number of the success of the distribution
pi: The success rate of the distribution

Return Values

The probability mass at x or false for failure.