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Date:         Fri, 8 Sep 2000 17:34:29 -0700
Reply-To:     Cassell.David@EPAMAIL.EPA.GOV
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "David L. Cassell" <Cassell.David@EPAMAIL.EPA.GOV>
Subject:      Re: Poisson Vs Negative Binomial Regressions
Comments: To: nwohaj@spectre.ag.uiuc.edu
Content-type: text/plain; charset=us-ascii

Ogbonnaya John Nwoha wrote: > How can I determine the better of a poisson regression result and a > negative binomial regression result. Attached are the outputs of an > actual regression. Which one is better?

I would hesitate to judge "better" based on mere statistical performance, particularly when your test statistics indicate that neither fit is really a lot better than the other. [I did have real trouble reading your attachments so I could have overlooked something - in future please do not use MIME in a mailing list which is gateway'd to a Usenet newsgroup!]

You'll be better off attacking this problem from a different direction. Or two. Here are two to start with. First, how do the residual plots look? Is one clearly a better fit than the other? Is one clearly meeting the underlying assumptions of the modeling process better than the other? And second [this is where I would actually start if I were consulting on this], what are the underlying features of your process? How do you expect the process to work, and hence which of the two models is a more rational model from the *scientific* perspective?

"Don't let statistics drive your science; let the science drive your statistics."

David -- David Cassell, OAO Corp. Cassell.David@epa.gov Senior computing specialist mathematical statistician


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