(PECL stats >= 1.0.0)
stats_dens_pmf_negative_binomial — Probability mass function of the negative binomial distribution
$x, float $n, float $pi): float
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.
xThe value at which the probability mass is calculated
nThe number of the success of the distribution
piThe success rate of the distribution
The probability mass at x or false for failure.