title: Intraclass correlation among measures related to alcohol use by school aged adolescents: estimates, correlates and applications in intervention studies.
abstract: School-based alcohol use prevention studies frequently employ designs in which schools are assigned to treatment conditions while observations are made on individuals. The nesting of schools within treatment conditions requires that the treatment effect be assessed against the between-school variance; unfortunately, that variance is usually larger than for randomly constituted groups and its precision is usually less than that for the within-school variance. These factors often combine to reduce power substantially. To address these problems, investigators need good estimates for the intraclass correlation which together with the number of observations per school determines the magnitude of the extra variation in the nested design. This article presents estimates of school-level intraclass correlation for measures related to alcohol use among ninth and twelfth grade students and discusses their use in planning new studies and analyzing previous or current studies.
authors.affiliation: Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis 55455, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Murray
authors.forename: B
authors.initials: B
authors.lastname: Short
mesh_terms: D000293:Adolescent; D000428:Alcohol Drinking / Q000453:epidemiology* / Q000517:prevention & control*; D000704:Analysis of Variance; D003627:Data Interpretation, Statistical; D005260:Female; D006266:Health Education / Q000458:organization & administration*; D006801:Humans; D008297:Male; D015397:Program Evaluation; D012107:Research Design; D012307:Risk Factors; D012572:School Health Services / Q000458:organization & administration*; D013334:Students / Q000523:psychology; D011795:Surveys and Questionnaires