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st: Bootstrap command when used with cluster and strata options


From   "Chris Frost" <Chris.Frost@lshtm.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Bootstrap command when used with cluster and strata options
Date   Wed, 23 Oct 2013 11:11:54 +0100

I think that there is a problem with the bootstrap command when used in conjunction with the "cluster" and "strata" options. The problem arises because the command "bootstrap, strata(group) cluster(id) idcluster(newid) ....." creates a variable "newid" which is only unique (at the cluster level) within each strata. For example if there are 1000 subjects (with multiple measures per subject) each with a unique id but in two equal size groups the above command will result in each bootstrap sample having only 500 values of newid with subjects being erroneously paired up: this will lead to incorrect variance estimates with a command such as bootstrap, strata(group) cluster(id) idcluster(newid): mixed outcome i.group || newid: 

Am I correct? Can this be fixed?
 
Chris Frost	



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