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Re: st: suest after svy:clogit

From   Maarten Buis <>
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

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 c.x2), group(id)

Hope this helps,

 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
Reichpietschufer 50
10785 Berlin
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