When Asked to Conduct an Experiment for His Research Methods

Multiple Choice

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.