Re: st: xtgee for skewed data

[José Maria Pacheco de Souza <jmpsouza@usp.br>]

Em 25/08/2011 08:15, Nick Cox escreveu:
> The discussion started by William Gould at
>
> http://blog.stata.com/2011/08/22/use-poisson-rather-than-regress-tell-a-friend/
>
> seems relevant. You have a massive spike in the distribution. No
> transformation will much affect that, as by Murphy's theorem a spike
> maps to a spike, and in any case there would be the usual argument
> about what to do with zeros. However, (importantly different here)
.....

Dear Statalisters:
I am not sure whether I can include this question in the thread above, 
but the subjet is related. If the interest is to run a linear regression 
 of a continuous variable as the response, say level of beta carothen, 
and for very small values the results are zero because the equipment can 
only show values equal or greater than .04, the use of -tobit- can be an 
statistical alternative?
Let´s assume there is no money to buy a better device.
Best regards,
josé maria
--
Jose Maria Pacheco de Souza
Professor Titular (aposentado), Colaborador Senior
Departamento de Epidemiologia/Faculdade de Saude Publica, USP
Av. Dr. Arnaldo, 715
01246-904  -  S. Paulo/SP - Brasil
fones (11)3061-7747; (11)3768-8612
www.fsp.usp.br/~jmpsouza
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