hypergeometric distribution

:  a probability function f(x) that gives the probability of obtaining exactly x elements of one kind and n - x elements of another if n elements are chosen at random without replacement from a finite population containing N elements of which M are of the first kind and N - M are of the second kind and that is equal to the number of combinations of M things taken x at a time multipled by the number of combinations of N - M things taken n - x at a time and divided by the number of combinations of N things taken n at a time