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Activity Number: 692
Type: Contributed
Date/Time: Thursday, August 8, 2013 : 10:30 AM to 12:20 PM
Sponsor: Section on Statistics in Epidemiology
Abstract - #308639
Title: Design Effects in Three-Level Studies
Author(s): Tina Cunningham*+ and Robert E. Johnson
Companies: Eastern Virginia Medical School and Vanderbilt University Department of Biostatistics
Keywords: Design Effect ; ICC ; Cluster
Abstract:

Experiments with three-level nested levels are frequently seen in different areas of research, such as health service and Epidemiology. For an example, consider a study in which new health interventions are randomized across health centers, while providers within each center will apply the intervention to individual subjects. Design and analysis of three-level study are more complicated than simple single level or two-level models since the multilevel nesting effect introduces more than one intracluster correlation (ICC). One way to account for this intracluster dependence is to factor in the design effect(variance inflation factor).We propose the formula for the design effect in three-level models using generalized least squares solution. The derived formula is a function of the two ICCs and the sample sizes of each level. We explore the changes that could occur in the design effect in different situations. To narrow the focus of the discussion, we limit our attention to continuous outcomes with identity link function and compound symmetric error structure. Examples will be given to demonstrate practical implication of the formulas.


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