setSize - any numeric expression or field containing a non-negative numeric expression

numberOfChoices - any numeric expression or field containing a non-negative numeric expression

number

This function is useful in statistics, combinatorics, and polynomial expansions. The values returned by this function are referred to as combination coefficients. They form Pascal’s triangle.

Combination(5;2) returns 10 for a set consisting of {a, b, c, d, e} because the unique choices when choosing two at a time are {ab, ac, ad, ae, bc, bd, be, cd, ce, de}.

(13 * 12 * Combination(4;2) * Combination(4;3)) / Combination(52;5) returns 0.00144057..., which is the probability of being dealt a full-house in 5-card poker (less than a 1% chance).