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st: xtpois versus xtnbreg


From   "Oord, A. van den" <A.v.d.Oord@tm.tue.nl>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: xtpois versus xtnbreg
Date   Mon, 22 Mar 2004 12:11:50 +0100

Hi All,

I have a data set where I count the number of patents for a group of 113
companies per year over a period of 12 years. For my analysis, I
currently use a random effects poisson model for panel data (the command
'xtpois'). However, to be certain that I am using the correct model, I
wish to determine whether my dependent variable is overdispersed or not.
In the case of overdispersion I have to use the random effects negative
binomial model for panel data (the command 'xtnbreg'). How can I
determine whether my dependent variable is overdispersed or not?

Thanks in advance,

Ad van den Oord

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