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st: gamma family - alpha and theta parameters - xtgee


From   "Guillermo A. Sandoval (UofT)" <guillermo.sandoval@mail.utoronto.ca>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: gamma family - alpha and theta parameters - xtgee
Date   Tue, 28 May 2013 23:36:31 +0000

Dear
I am using xtgee with gamma distribution. I understand that for gamma distribution, one needs to define the parameters alpha and theta, which define the shape of the distribution function. Please see http://en.wikipedia.org/wiki/Gamma_distribution. My variable is continuous (mortality rates in hospitals) and distributes pretty much like the one in wekipedia that says k=1 and theta=2. 

In xtgee, it looks like one cannot define these parameters. I guess my question is, is this necessary (if yes, how)? or xtgee  actually estimates them and I don't really need to worry about that?

Thanks in advance

Guillermo

----
Guillermo A. Sandoval
PhD Candidate in Health Services Research

Institute of Health Policy, Management and Evaluation
University of Toronto


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