If this is an issue, then I think it would much be easier
to work with log of 0, 20, etc. and -intreg- and thus an
implicit lognormal model.
Naturally log of 0 would be taken as missing.
Nick
[email protected]
Feiveson, Alan H. (JSC-SK311)
> One possible problem with using -intreg- is that it
> (-intreg-) assumes a
> normally distributed latent variable that you can only
> observe in terms
> of intervals. On the surface, it appears that hours of activity would
> not be normally distributed for fixed values of the covariate(s). A
> user-written ml-procedure with a nonnegative latent variable
> distribution such as Gamma, that allows interval censoring
> might be more
> appropriate. Perhaps it wouldn't be that difficult to modify
> intreg.ado
> for this purpose.
>
*
* 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/
