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st: nbreg proc genmod equivalency


From   "Victor M. Enciso M." <v.enciso-mora@postgrad.manchester.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   st: nbreg proc genmod equivalency
Date   Thu, 27 Nov 2008 12:03:57 +0000

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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