... The gamma function [not the Gamma -- note upper-case G -- which is related to the factorial] is one of those insanely useful functions that after one finds out about it, one wonders ?why haven?t we been using this all the time?? It is defined only on the positive non-negative real line, is a highly flexible function that can emulate almost any kind of skewness in a distribution, and is a perfect complement to the Poisson likelihood. ... Tags: conjugate , EotW , Equation , gamma , Poisson , prior . ...