Returns the negative binomial distribution, the probability that there will be number_f failures before
the number_s-th success, with probability_s probability of a success.
This function is similar to the binomial distribution, except that the number of successes is
fixed, and the number of trials is variable. Like the binomial, trials are assumed to be independent.
For example, you need to find 10 people with excellent reflexes, and you know the probability
that a candidate has these qualifications is 0.3. NEGBINOM.DIST calculates the probability that you will
interview a certain number of unqualified candidates before finding all 10 qualified candidates.