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st: Re: RE: panel normalisation before xtgee


From   Allison.Milner@student.griffith.edu.au
To   Garry Anderson <g.anderson@unimelb.edu.au>, "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: Re: RE: panel normalisation before xtgee
Date   Wed, 01 Apr 2009 08:05:48 +1000

Thanks for your help Garry,
do you mean that I should change the nb(#) rather than using the normalisation procedure?
Allison

----- Original Message -----
From: Garry Anderson <g.anderson@unimelb.edu.au>
Date: Tuesday, March 31, 2009 5:39 pm
Subject: RE: panel normalisation before xtgee
To: Allison.Milner@student.griffith.edu.au

> Hi Allison,
> 
> On another matter, be aware that f(nb) is forcing your negative 
> binomialparameter from xtgee to be k=1.
> Note that k is the recipricol of alpha from -nbreg-
> Variance = u(1+alpha.u) where alpha is reported from the -nbreg-
> command.
> 
> f(nb #) with a suitable value of # may give a better fit. # is alpha
> Garry
> 
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of
> Allison.Milner@student.griffith.edu.au
> Sent: Tuesday, 31 March 2009 5:59 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: panel normalisation before xtgee
> 
> Dear Statalist,
> 
> I am using xtgee (xtgee, f(nb) corr(ar1) vce(r)) to analyze an
> unbalanced panel data set (with 73 countries, 1980-2006). Someone
> suggested that I normalize my variables by subtracting the mean from
> each of my observations. 
> e.g. 
> YEAR        VARIABLE ONE
> year 1980  observation 1 for variable 1 - mean of 
> observation of
> variable 1 year 1981  observation 2 for variable 1 - mean 
> of observation
> of variable 1 year 1982  observation 3 for variable 1 - 
> mean of
> observation of variable 1
> 
> Is this necessary?  
> Any opinions on this subject would be great.
> Allison
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