Health Education & Behavior

s for Practice Notes and all correspondence concerning abstract review should be sent to Lisa D. Lieberman, Healthy Concepts, 29 Ardsley Drive, New City, NY 10956. Submissions can be mailed (include one hard copy and disk in Word format or Word Perfect) or sent by e-mail attachment to llhealth@optonline.net in Word format. Published manuscript length is approximately 300 words (excluding headings and contact information). Submitted manuscripts may be up to 500 words and will be edited for length and clarity. Include the following: name of initiative or program, contact person, sponsoring agency or agencies, address, and phone number. The program description should include the following headings: Objectives, Assessment of Needs, Program Strategy (e.g., risk reduction, community organizing, media advocacy, disease management, policy advocacy, coalition building, social support, etc.), Evaluation Approach, and Implications for Practitioners (including descriptions of any special challenges or unique circumstances that the project has overcome). Authors should not include evaluation results because Practice Notes is intended to describe processes and programs, not to assess outcomes. Submissions will be judged on applicability and utility to the health education practitioner, clarity of objectives, innovativeness and creativity, existence of evaluation plan, and potential replicability. Additional artwork, graphs, or tables may be submitted in camera-ready form. Health Education & Behavior (December 2001) Mur ay et al. / Dietary Intraclass Correlations Intraclass Correlation for Measures From a Middle School Nutrition Intervention Study: Estimates, Correlates, and Applications David M. Murray, PhD Glenn A. Phillips, MA Amanda S. Birnbaum, PhD, MPH Leslie A. Lytle, PhD This article presents the first estimates of school-level intraclass correlation for dietary measures based on data from the Teens Eating for Energy and Nutrition at School study. This study involves 3,878 seventh graders from 16 middle schools from Minneapolis–St. Paul, Minnesota. The sample was 66.8% White, 11.2% Black, and 7.0% Asian; 48.8% of the sample was female. Typical fruit and vegetable intake was assessed with a modified version of the Behavior Risk Factor Surveillance System questionnaire. Twenty-four-hour dietary recalls were conducted by nutritionists using the Minnesota Nutrition Data System. Mixed-model regression methods were used to estimate variance components for school and residual error, both before and after adjustment for demographic factors. School-level intraclass correlations were large enough, if ignored, to substantially inflate the Type I error rate in an analysis of treatment effects. The authors show how to use the estimates to determine sample size requirements for future studies. Nutrition intervention studies directed toward youth often use designs in which classrooms or schools are assigned to conditions, while observations are taken on individual students. Such studies are examples of a broader class of comparative studies called group-randomized trials. Quite generally, a group-randomized trial is a study in which identifiable groups are assigned to conditions while observations are taken on members of those groups. Studies with different units of assignment and observation exist in many disciplines and pose a number of design and analytic problems absent when individuals are randomized to conditions. The most important is that observations taken from members of the same identifiable group are likely to be correlated. This intraclass correlation (ICC) reflects a component of variance attributable to the groups in addition to the usual variation attributable to the members. It also violates the independence-of-errors assumption associated with the most familiar analytic methods. Simulation studies have shown that any analysis that ignores the ICC will have an inflated Type I error rate. Moreover, the David M. Murray and Glenn A. Phillips, Department of Psychology, University of Memphis, Memphis, Tennessee. Amanda S. Birnbaum and Leslie A. Lytle, Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis. Address reprint requests to David M. Murray, Department of Psychology, University of Memphis, 202 Psychology Building, Memphis, Tennessee 38152-3230; phone: (901) 678-5714; fax: (901) 678-4995; e-mail: d.murray@mail.psyc. memphis.edu. This research was supported by National Cancer Institutes Grant 1R01 CA71943-01A1. Health Education & Behavior, Vol. 28 (6): 666-679 (December 2001)