When a classifier threshold changes, sensitivity and specificity move in opposite directions. The receiver operating characteristic (ROC) curve makes that trade-off visible by plotting true positive rate against false positive rate across thresholds. section 5.5.5
Why both rates matter
A classifier that labels every record positive achieves sensitivity of 1, but also creates many false positives. Use the ROC curve to judge whether that trade-off is acceptable rather than treating high sensitivity as automatically successful. section 5.5.5
Figure 5.3 Sensitivity and specificity
Use the sensitivity-and-specificity figure to connect ROC axes with the underlying classification trade-off. section 5.5.5






