Fig. 3

Calibration plots. Assessment of the model’s internal validity using the development group (a), and external validity using the validation group (b): the mean predicted EGFR mutation probabilities plotted against the observed mutation probabilities with their 95% CI, shown in five groups created by the ranks of the predicted probabilities. Hosmer-Lemeshow test compares the observed and predicted probabilities: a p-value of > 0.05 indicates good calibration