To Test the Value of the Study Guide, Professor Lewis

Multiple Choice

To test the value of the study guide, Professor Lewis gives a free copy to the students sitting in the first two rows of class. Later she finds that these students got better grades than the students in the back of the room (who didn't get study guides) . What is wrong with this experiment?

A) lack of an independent variable
B) confusion of experimentation with correlation
C) lack of random assignment to groups
D) lack of a dependent variable