A cluster-adjusted sample size algorithm for proportions was developed using a beta-binomial model.

Full Abstract

OBJECTIVE:
The objective of the paper was to design a computer algorithm to calculate sample sizes for estimating proportions incorporating clustered sampling units using a beta-binomial model when information concerning the intraclass correlation is not available.

STUDY DESIGN AND SETTING:
A computer algorithm was written in FORTRAN and evaluated for a hypothetical sample size situation.

RESULTS:
The developed algorithm was able to incorporate clustering in estimated sample sizes through the specification of a beta distribution to account for within-cluster correlation. In a hypothetical example, the usual normal approximation method for estimation of a proportion ignoring the clustered sampling design resulted in a calculated sample size of 107, whereas the developed algorithm suggested that 208 sampling units would be necessary.

CONCLUSION:
It is important to incorporate cluster adjustment in sample size calculations when designing epidemiologic studies for estimation of disease burden and other population proportions in the situation of correlated data even when information concerning the intraclass correlation is not available. Beta-binomial models can be used to account for clustering, and design effects can be estimated by generating beta distributions that encompass within-cluster correlation.

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Author information

Author/s: Fosgate, G T (GT);

Affiliation: Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843-4458, USA. gfosgate(-atsign-)cvm.tamu.edu

Journal and publication information

Publication Type: Journal Article

Journal: Journal of clinical epidemiology (J Clin Epidemiol), published in England. (Language: eng)

Reference: 2007-Mar; vol 60 (issue 3) : pp 250-5

Dates: Created 2007/02/12; Completed 2007/03/19;

PMID: 17292018, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Algorithms
Binomial Distribution
Cluster Analysis
Communicable Diseases - epidemiology
Epidemiologic Studies

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