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.
Keywords
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to Journal of Clinical EpidemiologyAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Cluster trials in implementation research: estimation of intracluster correlation coefficients and sample size.Stat Med. 2001; 20: 391-399
- A comparison of confidence interval methods for the intraclass correlation coefficient in cluster randomized trials.Stat Med. 2002; 21: 3757-3774
- What is an intracluster correlation coefficient? Crucial concepts for primary care researchers.Ann Fam Med. 2005; 2: 204-208
- Prevalence estimation under heterogeneity in the example of bovine trypanosomosis in Uganda.Prev Vet Med. 1998; 36: 11-23
- Statistical methods for rates and proportions.3rd ed. John Wiley, Hoboken, NY2003 (p. 213)
- Study design and analytic methods for data collected from clusters of animals.Prev Vet Med. 1994; 18: 175-191
- The statistical analysis of multiple binary measurements.J Clin Epidemiol. 1988; 41: 899-905
- Estimating intraclass correlation for binary data.Biometrics. 1999; 55: 137-148
- Biostatistics: a foundation for analysis in the health sciences.7th ed. Wiley, New York1999 (p. 156)
- Sampling—how big a sample?.J Forensic Sci. 1999; 44: 750-760
- Categorical data analysis.2nd ed. Wiley-Interscience, New York2002 (p. 606)
- Hierarchical Bayesian model for prevalence inferences and determination of a country's status for an animal pathogen.Prev Vet Med. 2002; 55: 155-171
@Risk, version 4.5.2. Ithaca, NY: Palisade Corporation; 2002.
- Programming Research Group. Preliminary report: specifications for the IBM Mathematical FORmula TRANslating System, FORTRAN.The Corporation, New York1954
- Modified exact sample size for a binomial proportion with special emphasis on diagnostic test parameter estimation.Stat Med. 2005; 24: 2857-2866
Compaq visual Fortran: professional edition, version 6.6. Palo Alto, CA: Hewlett-Packard Company; 2000.
- Veterinary epidemiology.3rd ed. Blackwell Publishing, Ames, IA2005 (pp. 232–3)
- Guidance on public reporting of healthcare-associated infections: recommendations of the healthcare infection control advisory committee.Am J Infect Control. 2005; 33: 217-226
- Nosocomial infection update.Emerg Infect Dis. 1998; 4: 416-420
- Prevention and control of health care-associated waterborne infections in health care facilities.Am J Infect Control. 2005; 33: S26-S40
- Estimation of diagnostic-test sensitivity and specificity through Bayesian modeling.Prev Vet Med. 2005; 68: 145-163
Article info
Publication history
Published online: September 29, 2006
Accepted:
June 2,
2006
Identification
Copyright
© 2007 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
