I have one question: Many times, in order to test whether an outcome should be considered as "Signal" (S) or "Background" (B), we are using BDTs which we have trained on known outcomes... I was wondering though, the outcome of being S/B is binary : either it's signal or it's not... the only way I can interpret the BDT variable after that is as "how likely it is to be signal or not", since a particular cut on the BDT corresponds to some particular background rejection and signal efficiency (ROC curves). Is my interpretation correct? Would a "signal" object with a BDTscore=0.89 be a less likely signal than one with BDTscore=0.95 ? If not, then is there a way to compare the two events? I.e. the higher I place a cut on BDT the stronger/tighter signal events I'm selecting?