On the Joys of Missing Data

We provide conceptual introductions to missingness mechanisms-missing completely at random, missing at random, and missing not at random-and state-of-the-art methods of handling missing data-full-information maximum likelihood and multiple imputation-followed by a discussion of planned missing designs: Multiform questionnaire protocols, 2-method measurement models, and wave-missing longitudinal designs. We reviewed 80 articles of empirical studies published in the 2012 issues of the Journal of Pediatric Psychology to present a picture of how adequately missing data are currently handled in this field. To illustrate the benefits of using multiple imputation or full-information maximum likelihood and incorporating planned missingness into study designs, we provide example analyses of empirical data gathered using a 3-form planned missing design.