What this module builds
Performance judgement beyond accuracy.
Performance is not one number
Accuracy, sensitivity, specificity, ROC, AUC and calibration answer different questions. This module teaches students to read them together rather than choosing one headline metric.
Validation protects against overconfidence
A model can look excellent on the data that trained it and fail on new patients. Test sets, cross-validation and bootstrap validation help estimate future-patient performance more honestly.
Thresholds change decisions
A predicted risk is not a clinical decision until a threshold is chosen. Threshold choice changes false positives, false negatives and clinical workload.
Calibration matters in medicine
Clinical prediction models often communicate risk. If a model says 30% risk, the observed risk should be close to 30% among similar patients.
Leakage can destroy trust
If information from the future, the outcome process or the test set enters model fitting, the reported performance can become dangerously optimistic.
