# RE: st: RE: RE: Svytab subgroup analysis with more than two subgroups

 From "L Allen" To statalist@hsphsun2.harvard.edu Subject RE: st: RE: RE: Svytab subgroup analysis with more than two subgroups Date Wed, 23 Jul 2003 15:21:39 +0000

Doesn't this have the same effect as using an if restriction? If so, the manual warns that Stata will not produce correct statistics and variance estimates?

Richard Clerkin
Ph.D. Student
Indiana Nonprofit Project
Indiana University-Bloomington

From: "Sayer, Bryan" <BSayer@s-3.com>
To: "'L Allen '" <indiananonprofit@hotmail.com>, "'statalist@hsphsun2.harvard.edu '" <statalist@hsphsun2.harvard.edu>
Subject: RE: st: RE: RE: Svytab subgroup analysis with more than two subgroups
Date: Wed, 23 Jul 2003 09:34:56 -0400

This would appear to be one of the negative side effects to how Stata
handles subpop(). But you might try setting the value of the group var to
missing for values outside of the subpop(). In fact, manipulating missing
values is a general fix for many problems with subpop().

Bryan Sayer
Statistician, SSS Inc.

-----Original Message-----
From: L Allen
To: statalist@hsphsun2.harvard.edu
Sent: 7/23/03 9:14 AM
Subject: Re: st: RE: RE: Svytab subgroup analysis with more than two
subgroups

That is what I want. However, the problem I ran into when constructing
the
subgroup, both previously and as suggested below, is that the 3 groups
not
in the subgroup are still levels in the groupvar and generate a 0 count
in
half the cells in the table. With zeros in the marginals, a chi-square
cannot be computed.

Richard Clerkin
Ph.D. Student
Indiana Nonprofit Project
Indiana University-Bloomington

>From: Lee Sieswerda <Lee.Sieswerda@tbdhu.com>
>To: "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
>Subject: st: RE: RE: Svytab subgroup analysis with more than two
subgroups
>Date: Mon, 21 Jul 2003 09:31:24 -0400
>
>I'm not sure that I completely understand your problem either, but
>something
>like this:
>
>tab groupvar, gen(group)
>gen dichot = (group1==1 | group2==1 | group3==1)
>svytab groupvar catvar, subpop(dichot)
>
>would give you a chi-square test for the association between groupvar
and
>catvar for three out of your six groups. Is that not what you are
looking
>for?
>
>Lee Sieswerda, Epidemiologist
>Thunder Bay District Health Unit
>Lee.Sieswerda@tbdhu.com
>
>
>-----Original Message-----
>From: L Allen [mailto:indiananonprofit@hotmail.com]
>Sent: Monday, July 14, 2003 1:56 PM
>To: statalist@hsphsun2.harvard.edu
>Subject: st: Svytab subgroup analysis with more than two subgroups
>
>
>Dear Statalist,
>
>We have survey data with 39 strata. We have categorized the
respondents
>into 6 groups. This grouping was not used in the sampling design (it is
not
>one of our stratifying variables). We want to do a svytab on 3 of the
6
>groups against responses to a categorical variable; however, the survey
>manual warns us not to us an if restriction to select these three
groups
>because it will not produce correct statistics and variance estimates.
>However, the subpop() option does not appear to meet our needs either
>because we want to test the association among these three groups. Any
>suggestions on how to proceed would be appreciated.
>
>Richard Clerkin
>Ph.D. Student
>Indiana Nonprofit Project
>Indiana University-Bloomington
>
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