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Re: st: PWEIGHT question


From   "Michael I. Lichter" <mlichter@buffalo.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: PWEIGHT question
Date   Fri, 15 May 2009 13:40:06 -0400

If the weights were created based on externally-determined population totals rather than on the survey design, the weights are poststratification weights, not probability weights (pweights). The svy procedures allow poststratification weights (which can be set using -svyset-; see -help svyset-), but you would need to create a poststrata identifier variable (assuming you don't already have one) and transform the weights into cell counts. Simply treating the weights as pweights should yield very similar if not identical results compared to formally declared poststratification weights with svy procedures, and will in any event get you much more reasonable results than if you used standard SPSS weighting. (The SPSS Complex Samples add-on, however, does [mostly] what the Stata svy commands do.)

Michael

Charles Man@CCR wrote:

Dear subscribers,

I am new to STATA. I want to know how to use pweight option.

I have a small telephone survey dataset of 500 cases which were randomly drawn from a population of 7 million people. The dataset was weighted according to income and sex distributions of the population. In Stata, do I need to include [pw=weight] in all analyses? In SPSS, people simply choose WEIGHT BY and don’t have to be concerned about the weight type. However, in Stata, we have to determine which weight type is appropriate. Is it Pweight or Fweight useful in my situation? Which one is the most appropriate?

I look forward to your advice. Thanks a lot.

Best Regards,

Charles


--
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 125 / Phone: 716-898-4751 / FAX: 716-898-3536

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