Syntax: NgB(s, probability, stream)
The negative binomial distribution (discrete) with parameters s (> 0.0) and probability = p can be thought of as the distribution of the number of failures before the sth success in a sequence of independent Bernoulli trials, where success occurs on each trial with a probability of p and failure occurs on each trial with a probability of 1 - p. A negative binomial distribution with parameters s = 1 and probability = p is a geometric distribution with probability = p.
Stream allows you to specify the random number stream for the distribution. There are 215 streams. Stream 1 is the default. See Seeds or Appendix D of the User's Guide for more information.