Function negBinomCDF

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

j=0, k n+j-1, j p, n (1-p), j ???? In mathworld, it is j=0, k n+j-1, j-1 p, j (1-p), n

In a sequence of Bernoulli trials, this is the probability that k or fewer failures precede the n-th success.

The arguments must be positive, with 0 < p < 1 and r>0.

The Geometric Distribution is a special case of the negative binomial distribution.

geometricDistribution(k, p) = negativeBinomialDistribution(k, 1, p);

References

http://mathworld.wolfram.com/NegativeBinomialDistribution.html