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RE: st: RE: Fractional Logit


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Fractional Logit
Date   Sun, 30 Oct 2005 16:44:00 -0000

If that is a possibility, so also is the -betafit- 
of Stephen Jenkins et alius, downloadable from SSC. 

Nick 
n.j.cox@durham.ac.uk 

Clive Nicholas
 
> Rijo John replied to Nick Cox:
> 
> > Thanks Nick. I am trying to estimate the impact of spending on a
> > particular commodity (say X) on the purchase of other goods 
> and services.
> > So I have the share of, say commodity Y (Its share in 
> household budget)
> > as the dependent variable and the expenditure on commodity X along
> with
> > various control variables for household as explanatory 
> variables. This
> > can be a standrad OLS estimation. But since the depended 
> variable is a
> > fraction and  is bound between 0 and 1 we go for fractional 
> logit model.
> >
> > I hope this clarifies the problem. Given this I would like 
> to know what
> > would be the right choice of family and link in GLM.
> >
> > "family(gaussian) link(logit)" or "family(binomial) 
> link(logit)" or some
> > other combination?
> >
> > in "family(binomial) link(logit)" is it tru that stata 
> takes all values
> > other than 0 in the dependent variable as 1. If thats the 
> case it does
> > not take the budget share (absolute amount) information 
> into account. It
> > will only see if the budget share is absent or not.
> 
> Since your dependent variable is a fractional, or 'compositional',
> variable ranging continuously from 0 to 1, another 
> alternative is to use
> Sean 'Jack' Buckley's -mlbeta-. This allows maximum 
> likelihood estimation
> with Beta-distributed dependent variables, as well as 
> modelling separate
> equations for both a mean and dispersion effect. This routine is _not_
> downloadable from SSC, so type:
> 
> . net from http://www2.bc.edu/~bucklesj
> 
> and then click on -mlbeta-. Hope that helps.

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