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| From | Laurie Molina <molinalaurie@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | st: Bias in a zero truncated poisson |
| Date | Sun, 31 Oct 2010 10:11:35 -0600 |
Hi all, My dependent variable is a count data variable that takes only positive values. I am running: *** ztp depvar indepvars predict number sum depvar sum number **** but the mean of depvar is not the same as the mean of number. On the other hand if i run ****** poisson depvar indepvars predict number2 sum depvar sum number2 ****** the mean of depvar is the same as the mean of number2. Why is this happening? Aren't ztp estimates unbiased estimates? Thank you all as always... LM * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/