Describe the difference in roles assumed by the validation partition and the test partition.

The difference in roles assumed by the validation partition and the test partition is that the validation set is used to differ their performances and to select a model among various models (ANN), for instance, comparing ANN models with a different number of layers which are hidden. The test set, on the other hand, is used to get the character of the performance such as the accuracy (RMSE...). This set is not used in the building process of a model.