%0 Journal Article %1 Bra:2003:A-mi %A Braun, Thomas M. %D 2003 %J Statistical Modelling: An International Journal %K (Statistics), APPROXIMATION, ASYMPTOTIC CLUSTER Carlo MARGINAL MATHEMATICAL MODEL, MONTE POWER, SADDLEPOINT SAMPLE SIZE STOCHASTIC analysis, efficiencies method, processes, statistics, %N 3 %P p233 - %T A mixed model formulation for designing cluster randomized trials with binary outcomes. %V 3 %X Cluster randomized trials (CRTs) are unlike traditional individually randomized trials because observations within the same cluster are positively correlated and the sample size (number of clusters) is relatively small. Although formulae for sample size and power estimates of CRT designs do exist, these formulae rely upon first-order asymptotic approximations for the distribution of the average intervention effect and are inaccurate for CRTs that have a small number of clusters. These formulae also assume that the intracluster correlation (ICC) is the same for each cluster in the CRT. However, for CRTs in which the clusters are classrooms or medical practices, the degree of ICC is often a factor of how many students are in each classroom or how many patients are in each practice. Specifically, smaller clusters are expected to have larger ICC than larger clusters. A weighted sum of the cluster means, D, is the statistic often used to estimate the average intervention effect in a CRT. T

@article{Bra:2003:A-mi, abstract = {Cluster randomized trials (CRTs) are unlike traditional individually randomized trials because observations within the same cluster are positively correlated and the sample size (number of clusters) is relatively small. Although formulae for sample size and power estimates of CRT designs do exist, these formulae rely upon first-order asymptotic approximations for the distribution of the average intervention effect and are inaccurate for CRTs that have a small number of clusters. These formulae also assume that the intracluster correlation (ICC) is the same for each cluster in the CRT. However, for CRTs in which the clusters are classrooms or medical practices, the degree of ICC is often a factor of how many students are in each classroom or how many patients are in each practice. Specifically, smaller clusters are expected to have larger ICC than larger clusters. A weighted sum of the cluster means, D, is the statistic often used to estimate the average intervention effect in a CRT. T}, added-at = {2009-10-28T04:42:52.000+0100}, author = {Braun, Thomas M.}, bdsk-file-1 = {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}, bdsk-url-1 = {http://ezp1.harvard.edu/login?url=http://search.ebscohost.com.ezp1.harvard.edu/login.aspx?direct=true&db=aph&AN=11351503&site=ehost-live&scope=site}, biburl = {https://www.bibsonomy.org/bibtex/2ee13d146c9376b8942e052dfef03a0ef/jwbowers}, date-added = {2007-09-03 22:45:16 -0500}, date-modified = {2009-01-15 12:15:57 -0600}, interhash = {ca318e5164219b8cbeaee6f75858ca53}, intrahash = {ee13d146c9376b8942e052dfef03a0ef}, issn = {1471082X}, journal = {Statistical Modelling: An International Journal}, keywords = {(Statistics), APPROXIMATION, ASYMPTOTIC CLUSTER Carlo MARGINAL MATHEMATICAL MODEL, MONTE POWER, SADDLEPOINT SAMPLE SIZE STOCHASTIC analysis, efficiencies method, processes, statistics,}, local-url = {file://localhost/Users/jwbowers/Documents/PAPERS/Bra2003A%20mi.pdf}, number = 3, pages = {p233 -}, timestamp = {2009-10-28T04:42:57.000+0100}, title = {A mixed model formulation for designing cluster randomized trials with binary outcomes.}, volume = 3, year = 2003 }