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Re: st: svy subpop option and e(sample)


From   Richard Williams <richardwilliams.ndu@gmail.com>
To   statalist@hsphsun2.harvard.edu, statalist@hsphsun2.harvard.edu
Subject   Re: st: svy subpop option and e(sample)
Date   Fri, 27 May 2011 11:25:12 -0500

At 10:08 AM 5/27/2011, Steven Samuels wrote:
Hitesh

After reading Section 5.4 of Korn and Graubard (1999), I return to Stas's advice: you need a good reason not to do the correct analysis. Here lack of memory won't be a reason, for,as you have apparently surmised, you don't need to load the entire original data set. Instead create _one_ dummy observation for each PSU that contains no members of the sub-population. For this observation, set the value of all the analysis variables to zero or to some other convenient value.

Interesting. Would it be fairly straightforward to create an -svyextract- command then? It seems like such a command could be quite useful for those who would otherwise have to deal with massive data sets. Maybe even add a property to the svysettings so the dof would be right when analyzing the extract. This might be a good wish list item for Stata 12.

There is one more thing to do: in the -svyset- statement, use the -dof()- option to set the degrees of freedom to: number of PSUs with members of the subpopulation minus number of strata with observations in the sub-population (Korn & Graubard, 1999, p. 209).

Ref: Korn, Edward Lee, and Barry I Graubard. 1999. Analysis of Health Surveys. New York: Wiley.

Steve
sjsamuels@gmail.com

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