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st: stcox: bootstrap option produces LOWER standard error and WIDER ci95


From   mcculloc@berkeley.edu
To   "Statalist" <statalist@hsphsun2.harvard.edu>
Subject   st: stcox: bootstrap option produces LOWER standard error and WIDER ci95
Date   Thu, 30 Nov 2006 10:30:32 -0800 (PST)

Dear Statalist members, I apologize for this reposting. For some reason I
have been unsubscribed for several days.  Here's my question:

I'm using stcox to estimate survival with one binary covariate (tcm), with
the model:
 	stcox tcm

Perhaps I'm mistaken, but I was expecting the bootstrap option to produce
a higher standard error and wider ci95.

BOOTSTRAP     	MODEL	HR     CI95          	SE     p
NO			tcm		0.77   0.36, 1.67    	0.30   0.51
YES			tcm 		0.77   0.39, 1.55    	0.27   0.47

Can anybody suggest why that might be the case?



Best wishes,
Michael


____________________________________

Michael McCulloch
Pine Street Clinic
Pine Street Foundation
124 Pine Street, San Anselmo, CA 94960-2674
tel   	415.407.1357
fax 	415.485.1065
email:	mm@pinest.org
web:	www.pinest.org
 	www.pinestreetfoundation.org
 	www.medepi.net/meta





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