Standardized Effect Sizes for Preventive Mobile Health Interventions in Micro-randomized Trials
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Mobile Health (mHealth) interventions are behavioral interventions that are accessible to individuals in their daily lives via a mobile device. Most mHealth interventions consist of multiple intervention components. Some of the components are “pull” components, which require individuals to access the component on their mobile device at moments when they decide they need help. Other intervention components are “push” components, which are initiated by the intervention, not the individual, and are delivered via notifications or text messages. Micro-randomized trials (MRTs) have been developed to provide data to assess the effects of push intervention components on subsequent emotions and behavior. In this paper, we review the micro-randomized trial design and provide an approach to computing a standardized effect size for these intervention components. This effect size can be used to compare different push intervention components that may be included in an mHealth intervention. In addition, a standardized effect size can be used to inform sample size calculations for future MRTs. Here, the standardized effect size is a function of time because the push notifications can occur repeatedly over time. We illustrate this methodology using data from an MRT involving HeartSteps, an mHealth intervention for physical activity as part of the secondary prevention of heart disease.
KeywordsMicro-randomized trials Precision behavioral science Standardized effect size
Research presented in this paper was supported by the National Heart, Lung and Blood Institute under award number R01HL125440; the National Institute on Alcohol Abuse and Alcoholism under award number R01AA023187; the National Institute on Drug Abuse under award number P50DA039838; and the National Institute of Biomedical Imaging and Bioengineering under award number U54EB020404.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
Human Participants and/or Animals
This article does not contain any studies with animals performed by any of the authors. Informed consent was obtained from all individual participants included in the study of HeartSteps.
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