Javier wants to determine whether the presence of Tom Cruise in a movie increases the box office take. He randomly forms two groups of subjects. One group sees Mission Impossible III, starring Cruise, and the other group sees Barney's Big Adventure, without Cruise. Sure enough, the Tom Cruise movie is later rated as more enjoyable than the movie starring the purple dinosaur. Javier concludes that Tom Cruise movies are sure winners. What's wrong with this experiment?
a. The dependent variable--Tom Cruise versus Barney--is confounded with the content of the movie.
b. the independent variable--Tom Cruise versus Barney---is not the only factor changing across groups.
c. Nothing has been manipulated---its really a correlational study.
d. Experiments of this type require independent variables with at least three conditions.
b. The independent variables--Tom Cruise versus Barney---is not the only factor changing across the groups.