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Re: st: Using weights from the Current Population survey


From   David Kantor <dkantor@jhu.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Using weights from the Current Population survey
Date   Wed, 03 Jul 2002 13:53:11 -0400

At 12:18 PM 7/3/2002 -0500, Nammi Kandula wrote:
I am doing an analysis with the MARCH current population survey.
I am doing a person-level analysis.

If I use the wgt varaible, stata asks me what kind of weight this is.
Is it an analytic weight, pweight, fweight?

Should I use the weight in my regressions, or in my tab commands. Do i need
to transform the weight in any way?
My experience is that all weights in surveys from the U.S. Census Bureau are pweights.

You should specify them as pweights in regressions. (If you use them as aweight, the coefficients will be the same, but the variances and confidence intervals will be wrong. See the section in the user guide on Estimation, Weighted Estimation; that's U 26.12 in my ancient V5 manual.)

Better -- use svyreg and specify the strata and psu, if these are identified. Still, specify the weight as pweight.

For -tabulate-, pweight is not accepted. Use aweight or iweight; the proportions will not be affected by the choice, but iweight has the advantage that the "Freq." will be the weighted sums of the observations -- i.e., the estimated number of actual population in the given category. Be sure you have scaled the weight correctly at the outset, if there are any implied decimals in the raw data.

I hope this helps.
-- David K.

David Kantor
Institute for Policy Studies
Johns Hopkins University
dkantor@jhu.edu
410-516-5404

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