A professor wants to examine the effectiveness of a new teaching approach. She has a theory about how this new approach will work and will use a methodical approach to test her theory. Her 9:00 a. m. class will be exposed to the new method of viewing teaching tapes, while her 10:00 a. m. class will be exposed to traditional lectures. She will assess students' progress after six sessions. What method is the professor using to conduct her experiment?