3.4 Combining methods [...] are now compared with regard to their predictive performance. For this purpose, we apply the following general procedure: 1.

3.4 Combining methods [...] are now compared with regard to their predictive performance. For this purpose, we apply the following general procedure: 1. Form a training data set containing three out of four World Cups. 2. Fit each of the methods to the training data. 3. Predict the left-out World Cup using each of the prediction methods. 4. Iterate steps 1-3 such that each World Cup is once the left-out one. 5. Compare predicted and real outcomes for all prediction methods.