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Full-Text Articles in Rehabilitation and Therapy
Assessing Intervention Effects In A School-Based Nutrition Intervention Trial: Which Analytic Model Is Most Powerful?, Jessica B. Janega, David M. Murray, Sherri P. Varnell, Jonathan L. Blitstein, Amanda Birnbaum, Leslie A. Lytle
Assessing Intervention Effects In A School-Based Nutrition Intervention Trial: Which Analytic Model Is Most Powerful?, Jessica B. Janega, David M. Murray, Sherri P. Varnell, Jonathan L. Blitstein, Amanda Birnbaum, Leslie A. Lytle
Department of Public Health Scholarship and Creative Works
This article compares four mixed-model analyses valid for group-randomized trials (GRTs) involving a nested cohort design with a single pretest and posttest. This study makes estimates of intraclass correlations (ICCs) available to investigators planning GRTs addressing dietary outcomes. It also provides formulae demonstrating the potential benefits to the standard error of the intervention effect (σΔ) from adjustments for both fixed and time-varying covariates and correlations over time. These estimates will allow other researchers to use these variables to plan their studies by estimating a priori detectable differences and sample size requirements for any of the four analytic options. These methods …
Assessing The Most Powerful Analysis Method For School-Based Intervention Studies, Jessica B. Janega, David M. Murray, Sherri P. Varnell, Jonathan L. Blitstein, Amanda Birnbaum, Leslie A. Lytle
Assessing The Most Powerful Analysis Method For School-Based Intervention Studies, Jessica B. Janega, David M. Murray, Sherri P. Varnell, Jonathan L. Blitstein, Amanda Birnbaum, Leslie A. Lytle
Department of Public Health Scholarship and Creative Works
This article compares four mixed-model analyses valid for group-randomized trials (GRTs) involving a nested cohort design with a single pretest and a single posttest, the most common design used in GRTs. This study makes estimates of intraclass correlations (ICCs) available to investigators planning GRTs with alcohol, tobacco, and other drug measures as the outcomes of interest. It also provides formulae demonstrating the potential benefits to the standard error of the intervention effect of both adjustments for fixed and time-varying covariates, as well as correlations over time. These estimates will allow other researchers using these variables to plan their studies by …