A priori postulated and real power in cluster randomized trials: mind the gap

BACKGROUND: Cluster randomization design is increasingly used for the evaluation of health-care, screening or educational interventions. The intraclass correlation coefficient (ICC) defines the clustering effect and be specified during planning. The aim of this work is to study the influence of the...

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Detalles Bibliográficos
Autores principales: Guittet, Lydia, Giraudeau, Bruno, Ravaud, Philippe
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2005
Materias:
Research Article
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1190183/
https://www.ncbi.nlm.nih.gov/pubmed/16109162
http://dx.doi.org/10.1186/1471-2288-5-25
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author Guittet, Lydia
Giraudeau, Bruno
Ravaud, Philippe
author_facet Guittet, Lydia
Giraudeau, Bruno
Ravaud, Philippe
author_sort Guittet, Lydia
collection PubMed
description BACKGROUND: Cluster randomization design is increasingly used for the evaluation of health-care, screening or educational interventions. The intraclass correlation coefficient (ICC) defines the clustering effect and be specified during planning. The aim of this work is to study the influence of the ICC on power in cluster randomized trials. METHODS: Power contour graphs were drawn to illustrate the loss in power induced by an underestimation of the ICC when planning trials. We also derived the maximum achievable power given a specified ICC. RESULTS: The magnitude of the ICC can have a major impact on power, and with low numbers of clusters, 80% power may not be achievable. CONCLUSION: Underestimating the ICC during planning cluster randomized trials can lead to a seriously underpowered trial. Publication of a priori postulated and a posteriori estimated ICCs is necessary for a more objective reading: negative trial results may be the consequence of a loss of power due to a mis-specification of the ICC.
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spelling pubmed-11901832005-08-25 A priori postulated and real power in cluster randomized trials: mind the gap Guittet, Lydia Giraudeau, Bruno Ravaud, Philippe BMC Med Res Methodol Research Article BACKGROUND: Cluster randomization design is increasingly used for the evaluation of health-care, screening or educational interventions. The intraclass correlation coefficient (ICC) defines the clustering effect and be specified during planning. The aim of this work is to study the influence of the ICC on power in cluster randomized trials. METHODS: Power contour graphs were drawn to illustrate the loss in power induced by an underestimation of the ICC when planning trials. We also derived the maximum achievable power given a specified ICC. RESULTS: The magnitude of the ICC can have a major impact on power, and with low numbers of clusters, 80% power may not be achievable. CONCLUSION: Underestimating the ICC during planning cluster randomized trials can lead to a seriously underpowered trial. Publication of a priori postulated and a posteriori estimated ICCs is necessary for a more objective reading: negative trial results may be the consequence of a loss of power due to a mis-specification of the ICC. BioMed Central 2005-08-18 /pmc/articles/PMC1190183/ /pubmed/16109162 http://dx.doi.org/10.1186/1471-2288-5-25 Text en Copyright © 2005 Guittet et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Guittet, Lydia
Giraudeau, Bruno
Ravaud, Philippe
A priori postulated and real power in cluster randomized trials: mind the gap
title A priori postulated and real power in cluster randomized trials: mind the gap
title_full A priori postulated and real power in cluster randomized trials: mind the gap
title_fullStr A priori postulated and real power in cluster randomized trials: mind the gap
title_full_unstemmed A priori postulated and real power in cluster randomized trials: mind the gap
title_short A priori postulated and real power in cluster randomized trials: mind the gap
title_sort priori postulated and real power in cluster randomized trials: mind the gap
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1190183/
https://www.ncbi.nlm.nih.gov/pubmed/16109162
http://dx.doi.org/10.1186/1471-2288-5-25
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