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Inefficiency of randomization methods that balance on stratum margins and improvements with permuted blocks and a sequential method
Author(s) -
Kaiser Lee D.
Publication year - 2012
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.5345
Subject(s) - randomization , inefficiency , statistics , stratification (seeds) , econometrics , restricted randomization , mathematics , computer science , clinical trial , medicine , economics , seed dormancy , botany , germination , dormancy , biology , microeconomics
Stratified permuted blocks randomization is commonly applied in clinical trials, but other randomization methods that attempt to balance treatment counts marginally for the stratification variables are able to accommodate more stratification variables. When the analysis stratifies on the cells formed by crossing the stratification variables, these other randomization methods yield treatment effect estimates with larger variance than does stratified permuted blocks. When it is truly necessary to balance the randomization on many stratification variables, it is shown how this inefficiency can be improved by using a sequential randomization method where the first level balances on the crossing of the strata used in the analysis and further stratification variables fall lower in the sequential hierarchy. Copyright © 2012 John Wiley & Sons, Ltd.