Fig. 2From: Rank correlation under categorical confoundingHistograms of 10,000 p-values of a test of independence. Salary and Height are simulated as independent random variables with gender-specific marginal distributions. On the left panel, the tests of independence are based on Spearman’s rho calculated on the pooled data. On the right panel, a weighted version of the coefficient of correlation leads to an apparently unbiased testBack to article page