EXAMPLE 2 Antidepressants versus a placebo

Through a Freedom of Information Act request, two psychologists obtained 47 studies used by the Food and Drug Administration for approval of the six antidepressants prescribed most widely between 1987 and 1999. Overall, the psychologists found that there was a statistically significant difference in the effects of antidepressants compared with a placebo, with antidepressants being more effective. However, the psychologists went on to report that antidepressant pills worked 18% better than placebos, a statistically significant difference, “but not meaningful for people in clinical settings.’’