B. The ability of the Myc share in predicting the transcriptional outcome can be represented in terms of a Receiver operating characteristic (ROC) curve, which represents the Sensitivity (true positive rate) and Specificity (true negative rate) of a predictor (i.e. Myc share) in discriminating between two classes (i.e. up- and down-regulated genes), using different thresholds. The largest the area under the curve (AUC), the largest is the predictive power, in a scale from 0.5 (random classification: grey line) to 1 (perfect predictor). For each system, the dot corresponds to the variation of Myc at which promoters begin increasing their share of Myc binding. 