In the fall semester, a professor compared a lecture approach to teaching statistics (using a sophomore class) with a problem-oriented approach (using a senior class). Both sections were given the same final exam. The professor repeated the same experiment in the spring semester. This study shows a confounding of
a. test scores with teaching approaches.
b. class levels with test scores.
c. teaching approaches with class level.
d. semester with teaching approaches.
Question 2
Selection bias is a threat to internal validity arising from failure to use
a. a control group. c. reliable measuring instruments.
b. counterbalancing across conditions. d. random assignment.