Dr. Johansen randomly assigned subjects to three different groups during her last experiment. She then proceeded to give all the participants in the experiment a new study technique designed to enhance their learning for the upcoming test

What critical error did she make during her experiment?
A) She failed to identify the independent variable.
B) She failed to identify the dependent variable.
C) She failed to include an experimental group.
D) She failed to include a control group.

Answer: D
Rationale: A control group is the group that does not receive the treatment and therefore serves as a comparison for the experimental group(s). In this example, by giving all of the participants the new study technique, Dr. Johansen will not have a control group to compare the subjects with the new technique to. While the independent and dependent variables were not explicitly stated in the example, they are clearly the new study technique and the exam performance, respectively.