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Date:         Sat, 4 Jul 2009 13:19:59 -0400
Reply-To:     Wensui Liu <liuwensui@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Wensui Liu <liuwensui@GMAIL.COM>
Subject:      Re: Zero-inflated Poisson Regression
Comments: To: Newstat <chunyuanfei@gmail.com>
In-Reply-To:  <94c8fbb0-e46a-41b3-9e9c-eb8bd60fb43f@x6g2000prc.googlegroups.com>
Content-Type: text/plain; charset=ISO-8859-1

take a look at my sugi paper in 2008 "count data models in sas" and you should be able to find the answer.

On Sat, Jul 4, 2009 at 3:01 AM, Newstat<chunyuanfei@gmail.com> wrote: > I am using zero-inflated poisson regression to do data analysis. The > outcome is number of hospitalization. 70% have never been > hospitalized, 18% were hospitalized once, and 5% twice. The follow-up > period (age) varied among the subjects. I have several questions. > > 1. the estimates in the Poisson part were not robust even when I > slightly changed the categories of some covariants, for example, two > age groups (<25 and 25-29 years old) were combined. > > 2. When I compared with the point estimates from overdispersed, they > were even in the opposite direction. > > I am quite confused about which model I shall choose. Could you please > help me figure it out? Your response is highly appreciated. > > Vivian >

-- ============================== WenSui Liu Blog : statcompute.spaces.live.com Tough Times Never Last. But Tough People Do. - Robert Schuller ==============================


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