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Re: st: xtgee for skewed data


From   Austin Nichols <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: xtgee for skewed data
Date   Thu, 25 Aug 2011 10:23:03 -0400

José Maria Pacheco de Souza <jmpsouza@usp.br>:
Yes--see the third paragraph on page 5 of the presentation referenced
at the end of the blog post:
http://www.stata.com/meeting/boston10/boston10_nichols.pdf

2011/8/25 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

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