title: Primer: measuring the effects of treatment in clinical trials.
abstract: The results of clinical trials are often used as the basis for changes in clinical practice. Proper execution and interpretation of the results of trials are, therefore, of paramount importance to the welfare of patients. The results of a clinical trial are based on four key elements: the choice of the primary study end point, the method used to compare end points between groups, the clinically meaningful difference in the primary end point selected a priori by the investigators, and the power of the study to detect as statistically significant a difference between groups that is as large as the preselected clinically meaningful difference. These key elements directly follow from the primary hypothesis tested by the trial. This article reviews the basic features of these four elements, and the influence they have on the interpretation of clinical trials.
authors.affiliation: Intramural Research Program, National Institute of Arthritis and Musculoskeletal and Skin Disease, National Institutes of Health, Bethesda, MD, USA. wardm1@mail.nih.gov
authors.forename: Michael M
authors.initials: MM
authors.lastname: Ward
mesh_terms: D015510:Clinical Medicine / Q000379:methods*; D002986:Clinical Trials as Topic / Q000379:methods* / Q000706:statistics & numerical data; D003627:Data Interpretation, Statistical; D023381:Endpoint Determination; D006801:Humans; D018401:Sample Size; D016896:Treatment Outcome