Receiver operating characteristics (ROC) curve of the ABCD, ABC, ABD, ACD, and BCD models based on the test set (TS) and validation set (VS) of observations. The upper panels show the entire ROC curves, whereas the lower panels concentrate on the low FPR regions of each curve. The classification performances of each model is evaluated through the computation of the area under each of the TS–ROC and VS–ROC curves (AUC).