12 The model trained on PR05+SYN03 accounts for the most student learning variance in the test data, showing that the training data that is most similar to the test data will yield the highest generalizability.
the combined PR05+SYN03 corpora contains subjects drawn from the same subject pool (2005) as the SYN05 test data, and also contains subjects who interacted with the same tutor voice (synthesized) as this test data.