Discriminative power of the descriptor MFEahl. Red curve represents the CDF of the descriptor MFEahl for the taxonomic set Metazoa (3,902 miRNA hairpins). Blue curve represents the CDF of the SN-fitted distribution of the same descriptor in case of 100,000 randomly selected hairpins from the C. elegans genome. Green curve represents the discriminative power, calculated as sensitivity/(1.0-specificity). The fraction of hairpins in the S < 1 fraction is shaded (S < 1 cut-off at 95% of the CDF of known miRNA hairpins). The discriminative power at 95% sensitivity is shown by a green arrow (13.33). SN-fitted means are shown by red (0.44) and blue (0.18) arrows.