Document Detail


Calculating sample sizes for cluster randomized trials: We can keep it simple and efficient!
MedLine Citation:
PMID:  23017638     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
OBJECTIVE: Simple guidelines for calculating efficient sample sizes in cluster randomized trials with unknown intraclass correlation (ICC) and varying cluster sizes.
METHODS: A simple equation is given for the optimal number of clusters and sample size per cluster. Here, optimal means maximizing power for a given budget or minimizing total cost for a given power. The problems of cluster size variation and specification of the ICC of the outcome are solved in a simple yet efficient way.
RESULTS: The optimal number of clusters goes up, and the optimal sample size per cluster goes down as the ICC goes up or as the cluster-to-person cost ratio goes down. The available budget, desired power, and effect size only affect the number of clusters and not the sample size per cluster, which is between 7 and 70 for a wide range of cost ratios and ICCs. Power loss because of cluster size variation is compensated by sampling 10% more clusters. The optimal design for the ICC halfway the range of realistic ICC values is a good choice for the first stage of a two-stage design. The second stage is needed only if the first stage shows the ICC to be higher than assumed.
CONCLUSION: Efficient sample sizes for cluster randomized trials are easily computed, provided the cost per cluster and cost per person are specified.
Authors:
Gerard J P van Breukelen; Math J J M Candel
Related Documents :
23248578 - Quickbundles, a method for tractography simplification.
23751978 - On the thermodynamics of multilevel evolution.
14686448 - Multiscale entropy to distinguish physiologic and synthetic rr time series.
23540278 - A review of telemedicine business models.
15949918 - Generalized hamming networks and applications.
23874298 - Vbm with viscous fluid registration of gray matter segments in spm.
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of clinical epidemiology     Volume:  65     ISSN:  1878-5921     ISO Abbreviation:  J Clin Epidemiol     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-09-28     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8801383     Medline TA:  J Clin Epidemiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1212-8     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 Elsevier Inc. All rights reserved.
Affiliation:
Department of Methodology and Statistics, CAPHRI School for Public Health and Primary Care, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. Electronic address: gerard.vbreukelen@maastrichtuniversity.nl.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  Monte Carlo simulation of the cost-effectiveness of sample size maintenance programs revealed the ne...
Next Document:  Research on injury compensation and health outcomes: ignoring the problem of reverse causality led t...