Sample size calculations for micro‐randomized trials in mHealth. (28th December 2015)

• Record Type: Journal Article
• Authors: Liao, Peng; Klasnja, Predrag; Tewari, Ambuj; Murphy, Susan A.
• Is Part Of: Statistics in medicine. Volume 35:Number 12(2016)
• Page Start: 1944
• Page End: 1971
• Publication Date: 2015-12-28
• Subjects: mirco‐randomized trial -- sample size calculation -- health; Medical statistics -- Periodicals; Statistique médicale -- Périodiques; Statistiques médicales -- Périodiques; 610.727
• DOI: 10.1002/sim.6847
• Languages: English
• ISSNs: 0277-6715

Abstract

Abstract : The use and development of mobile interventions are experiencing rapid growth. In "just‐in‐time" mobile interventions, treatments are provided via a mobile device, and they are intended to help an individual make healthy decisions 'in the moment, ' and thus have a proximal, near future impact. Currently, the development of mobile interventions is proceeding at a much faster pace than that of associated data science methods. A first step toward developing data‐based methods is to provide an experimental design for testing the proximal effects of these just‐in‐time treatments. In this paper, we propose a 'micro‐randomized' trial design for this purpose. In a micro‐randomized trial, treatments are sequentially randomized throughout the conduct of the study, with the result that each participant may be randomized at the 100s or 1000s of occasions at which a treatment might be provided. Further, we develop a test statistic for assessing the proximal effect of a treatment as well as an associated sample size calculator. We conduct simulation evaluations of the sample size calculator in various settings. Rules of thumb that might be used in designing a micro‐randomized trial are discussed. This work is motivated by our collaboration on the HeartSteps mobile application designed to increase physical activity. Copyright © 2015 John Wiley & Sons, Ltd.