title: Assessing the most powerful analysis method for school-based intervention studies with alcohol, tobacco, and other drug outcomes.
abstract: 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 performing a priori power analyses for any of four common analytic options.
authors.affiliation: Department of Psychology, The University of Memphis, 202 Psychology Building, 3693 Norriswood, Memphis, TN 38152-3230, USA. j.janega@mail.psyc.memphis.edu
authors.forename: Jessica B
authors.initials: JB
authors.lastname: Janega
authors.forename: David M
authors.initials: DM
authors.lastname: Murray
authors.forename: Sherri P
authors.initials: SP
authors.lastname: Varnell
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Blitstein
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Birnbaum
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Lytle
mesh_terms: D000293:Adolescent; D000428:Alcohol Drinking / Q000517:prevention & control*; D000704:Analysis of Variance; D002648:Child; D003627:Data Interpretation, Statistical; D006293:Health Promotion / Q000379:methods; D006801:Humans; D015233:Models, Statistical; D016032:Randomized Controlled Trials as Topic / Q000379:methods; D012107:Research Design; D012572:School Health Services; D000074606:Smoking Prevention; D019966:Substance-Related Disorders / Q000517:prevention & control*