JSM 2005 Online Program

Abstract #303325

This is the preliminary program for the 2005 Joint Statistical Meetings in Minneapolis, Minnesota. Currently included in this program is the "technical" program, schedule of invited, topic contributed, regular contributed and poster sessions; Continuing Education courses (August 7-10, 2005); and Committee and Business Meetings. This on-line program will be updated frequently to reflect the most current revisions.

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Activity Number:	91
Type:	Topic Contributed
Date/Time:	Monday, August 8, 2005 : 8:30 AM to 10:20 AM
Sponsor:	General Methodology
Abstract - #303325
Title:	Optimality of Nested Designs with Equal and Unequal Cluster Sizes
Author(s):	Martijn Berger*+
Companies:	Maastricht University
Address:	Department Methodology and Statistics, Maastricht NL, 6200 MD, Netherlands
Keywords:	Optimal design ; random effect models ; D-optimality ; unequal clusters ; efficiency
Abstract:	In Health Sciences and Medicine, nested designs are encountered frequently. For example, in a multicenter clinical trial, patients are nested within clinics; in longitudinal studies, repeated measurements are nested within persons. The most appropriate statistical technique to handle the data from such studies is the multilevel model or the random effect model. In this paper, the optimality of such multilevel designs is examined. Two theorems concerning the D-optimality of equal cluster sizes when an intervention effect is randomly assigned to both the cluster (center) and person (patient) levels will be given. The relative efficiency of designs with unequal cluster sizes is computed for different values of the intraclass correlation coefficient and different cluster sizes. The results show that although a design with equal cluster sizes is nearly always optimal, the loss of efficiency for designs with unequal cluster sizes is not that large. It may be concluded that for many designs encountered in practice, a small increase of the number of clusters will compensate for the loss of efficiency when the designs have unequal cluster sizes.

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