Table 3 Characteristics of the measures implemented to evaluate the prediction ability of a model
Aspect | Measure | Characteristics |
|---|---|---|
Discriminative ability | Kaplan-Meier curves for risk groups | Better with greater distance between the Kaplan-Meier curves for the low- and high risk groups |
| Â | C-index | Estimates the concordance probability, i.e. the probability that the score correctly orders two patients with respect to their survival time; higher values correspond to better prediction |
| Â | K-statistic | Alternative to the C-index; works only under the proportional hazards assumption |
Calibration | Survival curves | Compares the observed survival function with the average predicted curve |
| Â | Calibration slope | Computes the regression coeffcient of the prognostic score as unique predictor; the best values are those close to 1; related to overfitting issues |
Overall prediction | Prediction error curves | Presents the Brier score versus time; the closer the curves are to the X-axis, the better the prediction |
| Â | Integrated Brier score | Computes the area under the prediction error curves; the smaller is the value, the better the prediction |