Dr. LaGuardia is a cognitive neuroscientist who is interested in the effect of brain concussions on the ability to recognize faces. He conducts a quasi-experimental study in which he examines football players before and after the regular season, using the Benton Facial Recognition Test (a published, widely used measure of oneâ€™s ability to recognize faces) to compare those who received concussions to those who did not. He finds that players who had concussions during the regular season performed worse on the Benton Facial Recognition Test than did players who did not experience concussions. Which of the following makes Dr. LaGuardiaâ€™s quasi-experimental study different from a correlational study?
A. He used a validated measure of the dependent variable.
B. He was able to confirm the occurrence of a concussion rather than relying on self-report.
C. He used a naturally occurring comparison group (i.e. players who did not suffer a concussion).
D. He used memebers of a real sports team rather than members of the general population.

Quasi-experimental study: In research methods, the term "quasi-experimental study" is described as a study that encompasses manipulation of the "independent variable" in the absence of a random assignment of subjects or participants to orders of conditions or different conditions.

Correlational study: In statistics, the term "correlational study" is described as one of the different types of study designs in which research or an investigator tends to comprehend the type of relationship that a naturally occurring variable possesses with one another.

In the question above, the correct answer is option D.