Regression Toward the Mean (5 of 6)

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These students, who presumably scored lower than expected on the SAT because of test anxiety, were administered the anti-anxiety drug before taking the SAT for the second time. The results supported the hypothesis that the drug could improve SAT scores by lowering anxiety: the SAT scores were higher the second time than the first time. Since SAT scores normally go up from the first to the second administration of the test, the researchers compared the improvement of the students in the experiment with nationwide data on how much students usually improve. The students in the experiment improved significantly more than the average improvement nationwide. The problem with this study is that by choosing students who scored lower than expected on the SAT, the researchers inadvertently chose students whose scores on the SAT were lower than their "true" scores. The increase on the retest could just as easily be due to regression toward the mean as to the effect of the drug. The degree to which there is regression toward the mean depends on the relative role of skill and luck in the test.