A Market Researcher Showed a Plain Print Ad of New

A market researcher showed a plain print ad of new brand of designer jeans to several groups of college students and asked the students to rate their quality. Then the researcher showed some other college students a print ad featuring movie star Scarlett Johansson wearing the new brand and asked the students again to rate the quality of the jeans. The marketer predicted that after viewing the ad featuring Johansson, the students' ratings of the jeans would be more positive than the other ones. In this experiment, students' ratings of the new blue jeans served as the

A) dependent variable.
B) independent variable.
C) social environmental force.
D) secondary data.
E) constraint.