Stephen Soldz wrote:
> A non-Stata question, though I'm using Stata for the anlysis. I'm analysing
> cost data and have used a GLM with gamma family and log link. The question I
> have is regards reporyting results. Should I exponentiate the coefficients
> (eform)? If so, any suggestions on how to describe this? Does anyone know of
> published examples I could refer to?
Did you ever get an answer?
The examples that crop up on the Web tend to either leave the coefficients
unexponentiated ( http://harrisschool.uchicago.edu/pdf/wp_03_13.pdf this is
Willard Manning, Anirban Basu & John Mullahy) or seem to use predictions (mu)
and talk about changes in them
( www.journals.uchicago.edu/CID/journal/issues/v33n12/001639/001639.text.html
and www.dianthus.co.uk/resources/sampleReport.pdf , and maybe
www.academyhealth.org/arm/abstracts/medicare.pdf ).
Log-gamma models are discussed in J. Hardin & J. Hilbe, _Generalized Linear
Models and Extensions_ (College Station, Texas: Stata Corporation, 2001),
pp. 69-71. They, too, didn't exponentiate the coefficients.
The one example of exponentiated coefficients that turned up (not exhaustive)
( www.mrc-bsu.cam.ac.uk/BSUsite/Publications/Preprints/glm_p6.pdf ) didn't give
them a very snazzy name, analogous to risk ratios or incidence rate ratios.
Joseph Coveney
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