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st: Re: Poisson Distribution


From   "Rodrigo A. Alfaro" <ralfaro76@hotmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: Poisson Distribution
Date   Mon, 15 May 2006 12:35:48 -0400

Dear Gauri:

1. Your model says noconstant, then you can use -noconstant- option.

2. From the help file...

    poisson fits a Poisson maximum-likelihood regression of depvar on 
varlist, where depvar is a
    nonnegative count variable.

Rodrigo.

----- Original Message ----- 
From: "Gauri Khanna" <gwkhanna@hotmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Monday, May 15, 2006 10:47 AM
Subject: st: Poisson Distribution


Dear Statalist,

I would like to run a Poisson Distribution for a count variable; number of
breakdowns(N) as a function of hours of tubewell operation (H).

The poisson distribution would be

exp(-Mu*H).[(Mu.H)^N]/N!

1. To do this, I would have to run the following regression:
Poisson Breakdowns Hours   - Is this correct?

However, I am not sure whether to have a constant term or not. So what
should I do?

2. I would like to estimate the parameter(Mu) using Max. Likelihood
techniques. Is this already produced from the simple Poisson regression
command?

As far as my understanding goes, the Poisson distribution utlitises the Max
Likelhiood technique and not OLS as the dependant variable takes on few
values that are non-negative integers.

Thank you for your help.

Regards,

Ms. Gauri Khanna

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