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From | "Laura R." <laura.roh@googlemail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: which -cmp- option to use for poisson model with count data? |
Date | Mon, 7 May 2012 16:58:07 +0200 |
Dear all, the distribution of the variable "number of experts" consulted is not "zero-inflated", but rather follows a normal distribution from 0 to 5. As there theoretically can be more than 5 experts, Nick sais, if I understand correctly, that this would be a hint to use Poisson model, as I would have to label the highest "category" "5 or more" in ordered probit. However, I have read that the events have to be independent of each other in the Poisson model, e.g. emergency room admission (taking David Roodman's example). This would be a reason for not using Poisson. E.g., deciding on getting a third child probably depends on how life is with 2 children --> ordered probit model. COnsulting another expert can also depend on what the last one had said. I think I will try the ordered probit model again, as this can be used within -cmp-, while the Poisson model cannot. If the parallel regression assumption or other assumptions for ordered probit models turn out to be violated, I will try the Poisson model, but then I have to come up with an idea similar to -cmp- that can be used with Poisson. Some people in this thread gave the hint on -gllamm- and -ssm-. I will keep that in mind and find out more about these models. Thank you all. LR * * 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/