Observed and Expected Proportion of Cesarean Deliveries in the Model Validation Group by Decile of Predicted Probability

<p>The white bars indicate the observed proportion and the black bars indicate the expected proportion of cesarean deliveries, based on estimates derived from logistic regression model fitted to the development group. Different graphs represent different procedures for selecting development and validation groups: (A) random selection, (B) selected on hospital throughput, (C) selected on deprivation category (Carstairs score), and (D) selected on year of delivery. Area under the ROC curve for each model is listed in <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0020252#pmed-0020252-t003" target="_blank">Table 3</a>.