Fisher's Exact Test Calculator

This tool runs Fisher's exact test on a two by two contingency table. Enter the four cell counts and it enumerates every table that shares the same row and column totals, returning the left tailed, right tailed and two tailed p values, the probability of your exact table, the sample odds ratio and the expected counts a chi-square test would have used. The p value is exact rather than approximate, which is what makes the test worth running when a cell count is small. Tables of up to one hundred thousand observations are handled without ever forming a factorial.