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From |
Lee Sieswerda <Lee.Sieswerda@tbdhu.com> |

To |
"'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: Using weights from the Current Population survey |

Date |
Wed, 3 Jul 2002 14:23:56 -0400 |

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 gives you asymptotic 95% CIs that will not cross 0 or 1 (which is good because you can't have less than 0 people enter a survey response, nor more than 100%). And to head off the next question, -svytab- won't allow you to specify only one variable in the command statement. If you want to tabulate the responses to a single question you have to create a constant (e.g., gen dum=1) and use 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, not -if- or -in-. And finally, you absolutely have to use the weights provided if you want the results to be representative of the population and not just the sample. I 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 in lightly-populated areas. To get around this problem in Canada, at least, for large government surveys we are provided with a data set of bootstrap weights from which to calculate bootstrapped standard errors. If you do not 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 Lee.Sieswerda@tbdhu.com www.tbdhu.com > -----Original Message----- > From: David Kantor [SMTP:dkantor@jhu.edu] > Sent: Wednesday, July 03, 2002 1:53 PM > To: statalist@hsphsun2.harvard.edu > 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 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 > > * > * For searches and help try: > * http://www.stata.com/support/faqs/res/findit.html > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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