In practice, there can be a classifier that gives far better performance at a specific acceptable threshold than an "optimal" classifier with better average performance across range of thresholds (higher AUC) but not so much at that threshold.
For example: Classifier 1: 80% TPR with 5% FPR; 95% TPR with 40%FPR AUC : .6 Classifier 2: 40% TPR with 5% FPR; 95% TPR with 20%FPR AUC : .9
- Classifier 1: 80% TPR with 5% FPR, 95% TPR with 40% FPR, AUC = 0.6
- Classifier 2: 40% TPR with 5% FPR, 95% TPR with 20% FPR, AUC = 0.9
Shouldn't iI use classifier 1 instead of classifier 2 if iI am operating around 5% FPR acceptable threshold?
Also, what should if I am allowed to run near 10% FPR?
- ( a ) Should iI just check TPR from both classifiers corresponding to 10% FPR and pick the classifier that has higher TPR?
- ( b ) Compute Or compute a partial area under curve tilluntil 10% FPR and pick the one with the highest?