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RE: st: Using weights from the Current Population survey

From   "Kandula, Nammi" <>
To   "'Lee Sieswerda '" <>, "''' '" <>
Subject   RE: st: Using weights from the Current Population survey
Date   Wed, 3 Jul 2002 13:43:33 -0500

The CPS does not provide PSU or strata- does this mean I cannot use svy


-----Original Message-----
From: Lee Sieswerda
To: ''
Sent: 7/3/2002 1:23 PM
Subject: RE: st: Using weights from the Current Population survey

A better option than using iweight or aweight with -tabulate- is to use
-svytab- and pweight. It has several advantages, one of which is that
you asymptotic 95% CIs that will not cross 0 or 1 (which is good because
can't have less than 0 people enter a survey response, nor more than

And to head off the next question, -svytab- won't allow you to specify
one variable in the command statement. If you want to tabulate the
to a single question you have to create a constant (e.g., gen dum=1) and
it as your second variable, as in:
svytab q1 dum, [options - lots of them]

Also, make sure you use the -subpop- option to specify subpopulations,
-if- or -in-.

And finally, you absolutely have to use the weights provided if you want
results to be representative of the population and not just the sample.
don't know about the CPS specifically, but it is unlikely that you'll be
provided with the psu and strata information because in well-conducted
surveys the clusters sampled are usually quite small and it would be
possible for a determined analyst to identify individuals - especially
lightly-populated areas. To get around this problem in Canada, at least,
large government surveys we are provided with a data set of bootstrap
weights from which to calculate bootstrapped standard errors. If you do
have access to the psu and strata information, then you might enquire if
such a beast is available for the Current Population Survey.

Best regards,

Lee S.

Lee Sieswerda, Epidemiologist
Thunder Bay District Health Unit
999 Balmoral Street
Thunder Bay, Ontario
Canada  P7B 6E7
Tel: +1 (807) 625-5957
Fax: +1 (807) 623-2369

> -----Original Message-----
> From:	David Kantor []
> Sent:	Wednesday, July 03, 2002 1:53 PM
> To:
> Subject:	Re: st: Using weights from the Current Population survey
> 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
> need
> >to transform the weight in any way?
> My experience is that all weights in surveys from the U.S. Census
> are pweights.
> You should specify them as pweights in regressions. (If you use them
> aweight, the coefficients will be the same, but the variances and 
> confidence intervals will be wrong.  See the section in the user guide
> Estimation, Weighted Estimation; that's U 26.12 in my ancient V5
> 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
> -- 
> i.e., the estimated number of actual population in the given category.
> sure you have scaled the weight correctly at the outset, if there are
> implied decimals in the raw data.
> I hope this helps.
> -- David K.
> David Kantor
> Institute for Policy Studies
> Johns Hopkins University
> 410-516-5404
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