The SSIR method is a variable selector based on the hypergeometric experiment (Mendenhall & Sincich, 1995). Briefly, given an urn containing red and green marbles, this probabilistic experiment consists of randomly selecting some of those marbles and, subsequently, assessing the probability associated with the distribution of red and green marbles which has been picked up. Specifically, the urn originally contains a marbles (b of them are green and the rest are red) and c are randomly selected. After the selection, one realizes that d of the marbles extracted are green. The probability for the described event follows the hypergeometric probability distribution: with d ≤ c ≤ a and d ≤ b ≤ a(1) where the minimum allowed value for d is max(0,c+b-a), and the maximum is min(b,c).