Teachers Jack Black and Shannon Shack want to increase the percentage of high school freshmen who ...

Teachers Jack Black and Shannon Shack want to increase the percentage of high school freshmen who pass an algebra exam (dependent variable). They conduct experiments on five sets of classes (named A to E) in Toronto area schools. They randomly assign students and give a pretest in September followed by a post-test the following January. The treatment is teaching method. The experimental groups are taught with special in-class demonstrations and pictorial games quizzes on computers, but no homework assignments, textbooks, or tests. The control groups are taught in the traditional manner with a textbook, homework, formulas on the blackboard, and tests.

Which results for a set of classes suggest that there might have been a “testing” effect from the pretest?
A) A
B) B
C) C
D) D
E) E