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st: Re: survey data - different results in version 8 and version 9?


From   "LUEDEMANN" <LUEDEMANN@ifo.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: survey data - different results in version 8 and version 9?
Date   Thu, 10 May 2007 14:46:03 +0200

Dear all,

I am using Stata version 9.2 (just updated it today!) and I am
re-running some analysis that I previously used in Stata 8.

The following command using version 8 code works, i.e. produces output
containing both regression coefficient estimates and standard errors:
. version 8
. svyset [pweight=newwgt], psu(psuid) strata(stratum)
. svyreg depvar $controls $dd $ddd


However, using the same data set and the following version 9 code

. svyset psuid [pweight=newwgt], strata(stratum)
. svy linearized: reg depvar $controls $dd $ddd

I get the following warning:

. Warning: variance matrix is nonsymmetric or highly singular

and output contains only regression coefficients (which exactly
correspond to those obtained from the version 8 command), but no
standard errors.

Does anyone know what changes have been implemented in Stata 9 as
opposed to Stata 8 concerning the Taylor linearized variance estimation?

Any help will be greatly appreciated. 
Thanks in advance,

Elke


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