Re: st: RE: nbreg proc genmod equivalency

["Victor M. Enciso M." <v.enciso-mora@postgrad.manchester.ac.uk>]

Thanks Kieran,

 this is the SAS code I'm using
=========================================================================
data dat2;
set victor.diar_completers;
lobs=log(At_Risk);
run;

proc genmod data=dat2;
   class Commid pair size trt;
   model EPISODES= pair trt / d=nb offset=lobs type1 type3;
   output out=victor.res3 pred=pred stdresdev=resids;
run;

quit;
=========================================================================
and the Stata command:

xi: nbreg  numepisodes i.pair i.studyortest, exposure( atriskdays)
or
xi: glm numepisodes i.pair i.studyortest, exposure( atriskdays)  
family(nb 0.1267885)
==============================================================================
where 0.1267885 is the dispersion parameter of the negative binomial  
obtained using nbreg.

Regards,

Victor

Quoting "Kieran McCaul" <kamccaul@meddent.uwa.edu.au>:

> Hi Victor,
>
> You might get a response I fyou sent the SAS code that generated this
> output and then the Stata code that you are trying to use.
>
> Kieran
>
> ______________________________________________
> Kieran McCaul MPH PhD
> WA Centre for Health & Ageing (M573)
> University of Western Australia
> Level 6, Ainslie House
> 48 Murray St
> Perth 6000
> Phone: (08) 9224-2140
> Fax: (08) 9224 8009
> email: kamccaul@meddent.uwa.edu.au
> http://myprofile.cos.com/mccaul
> _______________________________________________
> The fact that no one understands you doesn't make you an artist.
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Victor M.
> Enciso M.
> Sent: Thursday, 27 November 2008 9:04 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: nbreg proc genmod equivalency
>
> Hi everybody,
>
> I'm doing a negative binomial regression using Proc Genmod on SAS
> where this is part of the output
>
>
> Parameter   DF    Estimate       Error           Limits       Square
> Pr > ChiSq
>
> TRT   1      1     -0.2397      0.1102     -0.4557   -0.0237   4.73
> 0.0296
> TRT   2      0      0.0000      0.0000      0.0000    0.0000
> Dispersion   1      0.1268      0.0315      0.0651    0.1885
>
> NOTE: The negative binomial dispersion parameter was estimated by
> maximum likelihood.
>
>
>                      LR Statistics For Type 1 Analysis
>                           2*Log                 Chi-
>           Source       Likelihood        DF     Square    Pr > ChiS
>
>           Intercept     5189.2817
>           PAIR          5253.0473        34      63.77        0.0015
>           TRT           5257.5618         1       4.51        0.0336
>
>
>                       LR Statistics For Type 3 Analysis
>
>                                    Chi-
>           Source           DF     Square    Pr > ChiSq
>
>            PAIR             34      65.03        0.0011
>            TRT               1       4.51        0.0336
>
>
> I'm trying to reproduce this analysis in Stata but I don't know how to
> get the Type 1 and Type 3 Statistics. Anybody knows how to do this?
>
> Another question is why are the p-values of the contrast of tratment 1
> wrt to treatment 2 (0.0296) and the one given for TRT (0.0336)
> different?
>
> Thank you very much.
>
> Victor Enciso
>
>
>
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--
Víctor M. Enciso M.
School of Mathematics
The University of Manchester
C24 Ferranti Building
PO BOX 88
M60 1QD
Manchester, UK
Ext: 55820


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