When asked to conduct an experiment for his Research Methods class, Santiago had 10 of his friends self-report on the frequency of their exposure to movie violence, as well as their typical level of aggression. Based on his results he concluded that watching violent movies causes people to be more aggressive. Santiago's teacher tells him that he has failed to conduct an experimental study. Why wouldn't this study be considered an experiment?
A) He fails to establish covariation, which is a criterium for causation.
B) There is no control group.
C) Self-report measures are unreliable.
D) This study is unable to assess gender differences in aggression.

Question

Quizplus · Accepted Answer

There is no control group. A control group is necessary in an experimental study in order to establish causality by demonstrating that the changes in the dependent variable (in this case, aggression) are only due to the manipulation of the independent variable (in this case, exposure to movie violence). Without a control group, it is impossible to rule out other potential factors that may have impacted the results. In this case, it is possible that those who watched more violent movies were already more aggressive to begin with.

When Asked to Conduct an Experiment for His Research Methods