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st: Survey variance estimates - large software differences


From   "Levinson, Arnold" <Arnold.Levinson@ucdenver.edu>
To   "'Statalist'" <statalist@hsphsun2.harvard.edu>
Subject   st: Survey variance estimates - large software differences
Date   Tue, 30 Jun 2009 10:41:37 -0600

Survey analysis experts:
I have data from a stratified two-stage school survey. The first stage sampled schools within strata, the second sampled classrooms within selected schools.

When estimating variables of interest at the school level, I get hugely different variance estimates running Stata vs. SAS or SUDAAN. Stata's estimates are generally a lot smaller than SAS's or SUDAAN's, and the latter to are similar or identical to each other. 

My Stata svyset statement is:

svyset skulid [pw=skulwt], strata(strat) fpc(fpc) || classid

My SAS/SUDAAN design statements are the equivalent.

Any idea of what's going on here?
Thx...arnold
Arnold H. Levinson, PhD
Assistant Professor of Community and Behavioral Health
Colorado School of Public Health
Director, Tobacco & Amendment 35 Program Evaluation Group (TPEG, APEG)
13001 E. 17th Place, Mail Stop F542
P.O. Box 6508, Aurora CO 80045
Arnold.Levinson@uchsc.edu
voice: 303-724-3541
fax:    303-724-3544




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