Performance of three different logistic models p(I_main|counts) to predict a cluster as selected given the values of surface brightness in radial bins. The plain black line is obtained with a model using surface brightness values in 7 annuli for each of the 5 sky components. The dot-dashed line is for a model taking as input both cluster and background counts within 90″. The dashed grey line stands for a model using as input only the 90″ cluster counts. Each precision-recall curve results from model evaluations on the test sample. It is obtained by varying the threshold over which a cluster should be considered as selected and counting the number of true positives (TP), false negatives (FN) and false positives (FP).