CONTRASTING CLINICAL AND STATISTICAL SIGNIFICANCE WITHIN THE RESEARCHSETTING

When designing a clinical trial or study, the value of the following i nterrelated parameters should be determined prior to collecting data: clinical significance, statistical significance, power, and sample siz e. Too often, clinical importance and the other design issues are igno red and only statistical significance dictates the conclusions of the study. In order to evaluate the frequency that each of these design pa rameters is addressed in the published literature, the topic of pulmon ary function tests (specifically forced vital capacity) was chosen, an d all relevant articles for one year (1990) were identified using Minn esota MEDLINE. A total of 121 articles met the selection criteria and were reviewed. Of all the articles, 13.2% discussed clinical significa nce, 21.5% discussed sample size, and only 5.0% addressed statistical power. As expected, the majority of the articles (92.6%) discussed sta tistical significance (P values). None of the articles mentioned all f our factors. When choosing the level of clinical significance several methods may be used. Such might be well established in certain clinica l areas or available from previous publications and references or they may be attainable from pilot study data and, in the absence of any pr ior information, a clinician may use personal experience. To minimize subjectivity, the clinical effect-size can be based on the population distribution of the measurement of interest. (C) 1993 Wiley-Liss, Inc.