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RE: st: Using survey weights in regression models


From   Richard Williams <Richard.A.Williams.5@nd.edu>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: Using survey weights in regression models
Date   Thu, 27 Nov 2003 15:40:30 -0500

At 11:00 AM 11/27/2003 -0500, Lee Sieswerda wrote:
Interesting discussion. It raises another question for me, which is, if one
wants to use weights for post-stratification purposes only in a survey that
is otherwise conducted using SRS (e.g., to make, say, basic demographic
factors like age and sex match known population values in order to try to
get unbiased prevalence estimates), does one need to use the -svy-
functions? I thought that I had read somewhere that if weights were used in
this way, then one could think of them as aweights rather than pweights to
avoid having to use robust standard errors? But based on the discussion
below, maybe that is incorrect?
If I am reading the Stata manuals right (specifically, p. 346 of the Stata 8 User's guide, section 30.2) post-sampling adjustments should be handled via pweights rather than aweights, and pweights will use robust errors. Further, Stata's description of aweights does not sound consistent to me with what you are describing. (However, given that I've never actually used the svy commands, you may not want to accept me as the ultimate authority on this.)

Sections 23.16.2 and 23.16.3 of the Users Guide discuss analytic weights versus sampling weights (pweights). It notes that aweights have often been used when pweights should have been used instead.

One problem with starting discussions like this on Thanksgiving is that many of the people who know for sure what the right answers are are busy with other things today! Hopefully someone will eventually correct me if I am way off base here.


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