Three Way Split Approach. A) Three-way split of the full sample data. B) - Explanation of how the three-way split is incorporated into the MDR method. First the sample data is randomly split into 3 intervals with representative numbers of cases and controls in each interval. MDR is performed on each of the three splits with all possible models considered in the training set, the top x models considered in the testing set, and the final model considered in the validation set for each k.