scipy.special.nbdtr

scipy.special.nbdtr(k, n, p) = <ufunc 'nbdtr'>

Negative binomial cumulative distribution function

Returns the sum of the terms 0 through k of the negative binomial distribution:

sum((n+j-1)Cj p**n (1-p)**j,j=0..k).

In a sequence of Bernoulli trials this is the probability that k or fewer failures precede the nth success.