Fig. 5. Distributions of P values in relation to the ₀ statistic [the overall proportion of true null hypotheses (Storey and Tibshirani, 2003; Storey, 2003)] for the correlations in Tables 3, 4, 5. The bin size is.05; ₀ is shown as broken lines. A random set of P-values would produce a flat histogram with all bins showing a relative frequency close to 1.0; the presence of non-null hypotheses (i.e. significant tests after accounting for Type 1 errors) is indicated by high relative frequencies in the left-most bin. Values of ₀ were computed with the R program `Qvalue'.