Search efficiency for E. coli Fur sites in a skewed random background. ROC curves for search methods trying to locate 45 Fur binding sites on randomly generated backgrounds. The ROC curve depicts the mean and standard deviation of three independent experiments (searches against three independently genrerated backgrounds). The plot is scaled to encompass a 1/10 true to false positive ratio (450 false positives) in the equiprobable background. RE' results, which completely overlap RE · BvH ones, are not shown for clarity. The RE profiles for Fur against the different backgrounds are shown in the bottom-right inset.