Jack wants to test a new teaching technique - he expects the new method to increase test scores compared to the old method - so he uses the old technique for one week, gives an exam, then uses the new technique the next week in the same class, gives an exam that is assumed to be equal in difficulty to the first exam, and measures the difference between the two exam scores for each of his students. His class had 20 students in it, the average change score was +3.8 points (new method score - old method score), and the SS of these 20 change scores was 1520. What should Joe conclude about the new method?