Hypergeometric Distribution
From charlesreid1
Hypergeometric distribution counts the number of ways you can obtain particular target values when sampling from a population without replacement.
This describes many systems, most notably a deck of 52 Cards and dealing e.g. poker hands.
Hypergeometric distribution:
$ \dfrac{ \binom{K}{k} \binom{N-K}{n-k} }{ \binom{N}{n} } $
wehere:
$ \begin{align} K &=& \mbox{Number of successful trials} \\ N &=& \mbox{Popullation size} \\ k &=& \mbox{Number of targets for trials} \\ n &=& \mbox{Sample size} \end{align} $