Paula examined differences in college persistence between students who took the SAT either before their junior year or during their junior year of high school. She compared students with the same score and found that students who had taken the SAT before their junior year of high school were more likely to stay in college than those who had taken the SAT during their junior year. Paula employed which method for controlling the extraneous variable, performance, in her study?

Manipulation of independent variable

Comparing homogenous subgroups

Matching

Analysis of covariance (ANCOVA)