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From |
"Michael I. Lichter" <mlichter@buffalo.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Analyzing a subpopulation in Stata 10.1 |

Date |
Tue, 30 Jun 2009 15:48:22 -0400 |

Jeff,

In any event, I'll take a look at -svygen-. Thanks again to you, and also to Figen. Michael Jeff Pitblado, StataCorp LP wrote:

The thing to keep in mind here is that the poststratification adjustment must be applied to the entire estimation sample. It is not possible to reweight at the subpopulation level unless there is poststratification information at that level; i.e. if we had the postratum population sizes for the four cells defined by sex and native status. In table T3, -svy: tabulate- applies the weight adjustment to the 184 observations in the estimation sample. The only way to prevent that is to fix the adjusted weights ahead of time (see -help svygen-), but that isn't always a good solution. The poststratified sampling weights are designed to reduce bias in the point estimates; however, with the postratum ID's -svy linearized- can produce more efficient variance estimates than without. Ultimately, it is the researcher/data-analyst that has the responsibility and power to choose which analysis is most appropriate for themselves. I can imagine real survey data where there are any number of different poststratification adjustments one could apply for a given analysis. Some will make much more substantive sense than others. Suppose we had a variable called -ns_postid- that simultaneously identified the native status and sex of each individual in the dataset, and another variable called -ns_postw- that contained the population size for the corresponding group. I think it is clear that this poststratification information could be applied more broadly than the one in Michael's simulate dataset. --Jeff jpitblado@stata.com PS. There is an undocumented -svygen- command that will generate poststratification adjusted samling weights; see -help svygen-. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

-- Michael I. Lichter, Ph.D. <mlichter@buffalo.edu> Research Assistant Professor & NRSA Fellow UB Department of Family Medicine / Primary Care Research Institute UB Clinical Center, 462 Grider Street, Buffalo, NY 14215 Office: CC 126 / Phone: 716-898-4751 / FAX: 716-898-3536 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: Analyzing a subpopulation in Stata 10.1***From:*jpitblado@stata.com (Jeff Pitblado, StataCorp LP)

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