Supplementary information: ‘Random forest’, ‘Interpreting confusion matrices’, and ‘Used questionnaire’. Supplementary tables and figures: Table S1. Overview of variables measured by the questionnaire. Table S2. Performance of the total RF model with ‘intention request’; confusion matrix. Table S3. Performance of the total RF model with ‘intention 70’; confusion matrix. Figure S1. Variable importance analysis performed by RF for ‘intention 70’ (n = 303). Figure S2. Result of restricted forward feature selection with RF for ‘intention 70’. Table S4. Performance of the RF model with the top 10 variables for ‘intention 70’; confusion matrix. Table S5. Marginal probabilities of the top 10 variables in relation to ‘intention 70’. Figure S3. Variable importance analysis performed by RF for ‘intention 70’, including missing values as category (n = 379). Table S6. Performance metrics of all RF models. (DOCX 686 kb) ...