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Re: Subject: st: Is it necessary to have some variable for exposure in xtnbreg


From   Indu Khurana <indu.statauser@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: Subject: st: Is it necessary to have some variable for exposure in xtnbreg
Date   Wed, 15 Sep 2010 16:37:10 -0400

Thanks Joseph!!
That works.

On Wed, Sep 15, 2010 at 3:52 PM,  <jhilbe@aol.com> wrote:
> I get the digest, which is a day later, so someone may have already answered
> this query, in which case I
> apologize for the repetition.
>
> You do not need to have an exposure variable for xtnbreg. You do need,
> however, a variable that identifies
> the panel structure of the model, whether it be a GEE, random effects, or
> fixed effects model.  Standard Poisson
> and negative binomial models do not have to have an exposure either, which
> is simply another word for
> an offset where the offset variable is logged.
>
> Joseph Hilbe
>
>
>
>
>
>
> Date: Tue, 14 Sep 2010 20:33:33 -0400
> From: Indu Khurana <indu.statauser@gmail.com>
> Subject: st: Is it necessary to have some variable for exposure in xtnbreg
>
> Dear Statalisters,
>
> I have a count data on number of patents which is the dependent
> variable (panel setting). Right hand side variables include Employee
> well being and debt-equity ratio. The data on patents has a lot of
> zeros. Although ZINB could have been an option but I am using fixed
> effects. Therefore I decided to settle with negative binomial, fixed
> effects - xtnbreg
>
> My question is: Is it necessary to have some variable for exposure in
> xtnbreg?
>
> The data is on 5000 firms for 5 years which all came into existence at
> the same time in 2004. So basically they all have the same exposure.
> And there is no information on month of the the year.
> There is no other time dimension which can be used to fit in exposure.
>
> I was thinking of the following options:
> 1. To ignore exposure variable all together
>    Which I am not sure of whether it is correct.
> 2. To include number of years of owner's education to fill as exposure.
>
>
>
> Please suggest.
>
> Thanks
>
> Indu Khurana
>
>
>
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