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Re: st: logY, Tobit and the prediction of Y
firstname.lastname@example.org wrote on 23/04/2003 13:18:03:
> My initial model is:
> Y = a + b1x1 + controls + e
> where Y is expenditures on a commodity and x1 is income.
> Since there are a lot of zeroes, I use the Tobit apporach. However, since
> the log-linear model performed better than the linear, I use the former
> (Before the log transformation of Y, I follow convention and set zeroes
> Accordingly, the estimated Tobit model is:
> logY = a + b1x1 + controls + e
> The problem:
> I want to predict the value of Y (not logY) for certain values of income
> (and put it in a graph); that is, both the conditional Y (i.e. the Y
> that the threshold value of 0 was passed) and the unconditional (latent)
> value of Y.
> Does anyone know how to do this?
> Best regards,
> Christer Thrane
> Lillehammer University College
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
The prediction of Y from your model would simply be the exponential of the
However, you should note that the log of zero is minus infinity, so in your
log model no observations where Y is zero will be included. Is this really
what you want?
* For searches and help try: