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Re: st: suest after svy:clogit


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: suest after svy:clogit
Date   Fri, 17 May 2013 13:14:56 +0200

On Thu, May 16, 2013 at 6:31 PM, Klaus Nowotny wrote:
> I am having troubles using suest to test the equality of coefficients across
> two groups after svy:clogit. My survey data is set up as follows:
>
> svyset id [iw=weight]

To quote -help weight-: "iweights, or importance weights, are weights
that indicate the "importance" of the observation in some vague sense.
 iweights have no formal statistical definition; any command that
supports iweights will define exactly how they are treated.  Usually,
they are intended for use by programmers who want to produce a certain
computation."

So using iweights for a statistical analysis is almost certainly a mistake.

> I then estimate the model for two subgroups:
>
> svy, subpop(if group==1): clogit choice x1 x2, group(id)
> est sto group1
> svy, subpop(if group==2): clogit choice x1 x2, group(id)
> est sto group2
>
> To test for the equality of the coefficients of x1 across the two groups I
> follow the Stata reference manual for suest and enter
>
> suest group1 group2
>
> but Stata returns "r(198); option cluster() is not allowed with svy results"
> although I never entered the cluster option anywhere.

Why not just estimate the entire model in one go?

svy : clogit choice i.group##(c.x1 c.x2), group(id)

Hope this helps,
Maarten

 The same occurs if I
> try the alternative procedure suggested in the reference manual:
>
> clogit choice x1 x2 if group==1 [iw=weight], group(id)
> est sto group1
> clogit choice x1 x2 if group==2 [iw=weight], group(id)
> suest group1 group2, svy
>
> Why do I keep getting this error message? Any help would be greatly
> appreciated!
>
> Thanks,
> Klaus
>
> --
> Klaus Nowotny
> University of Salzburg
>
> *
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--
---------------------------------
Maarten L. Buis
WZB
Reichpietschufer 50
10785 Berlin
Germany

http://www.maartenbuis.nl
---------------------------------
*
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