Best (but oft-forgotten) practices: expressing and interpreting associations and effect sizes in clinical outcome assessments

This article reviews methods used to facilitate the interpretation and evaluation of group-level differences in clinical outcome assessments. These methods complement and supplement tests of statistical significance. Examples, including studies in nutrition, are used to illustrate the application of the interpretation methods for group level comparisons from experimental or observational studies. In addition, specific pitfalls of evaluating change in meta-analysis studies are described. A set of recommendations is provided. This review is intended as an introduction for the novice and as a refresher for the experienced researcher.