Issues in Randomization Outline
Issues in Randomization Outline
Issues in Randomization Outline
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Stratified Sampl<strong>in</strong>g• Select <strong>in</strong>dependent samples• Number of subpopulations,groups, strata with<strong>in</strong> thepopulation• Might ga<strong>in</strong> efficiency if donejudiciouslyCluster Sampl<strong>in</strong>g• Sample <strong>in</strong> groups• Need to look at <strong>in</strong>tra-clustercorrelation<strong>Randomization</strong> Conclusions• Permuted block randomization– Stratified by site– Appropriate to sample size– Block size(s) appropriate to sample size• Randomize smallest <strong>in</strong>dependent element atlast possible second• Mask<strong>in</strong>g/bl<strong>in</strong>d<strong>in</strong>g is also key• ITT (<strong>in</strong>tent to treat) analysis• Analyze as you randomize• Proper documentation and implementation24