Research and Statistics: Understanding and Identifying Bias in Research Studies

You are seeing a healthy 18-year-old patient who is interested in contraception and, specifically, the “Depo shot” or medroxyprogesterone. The information you have gathered from her during your visit and her medical history suggest that she is a good candidate. You take a few minutes out of the visit to review the literature for issues of safety. Most of the articles and reviews suggest that medroxyprogesterone is a good choice for healthy young women, but a recent study shows an association between medroxyprogesterone and the development of hypertension. You look more closely at the study and discover that the young women taking medroxyprogesterone had their vital signs (including blood pressure) checked every 3 months when they came in for the medroxyprogesterone injection. The other women included in the study for comparison only had their vital signs checked every year at annual health supervision visits. You are unclear about whether the...