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From |
"Lachenbruch, Peter" <Peter.Lachenbruch@oregonstate.edu> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: Zero-truncated Negative Binomial convergence |

Date |
Tue, 17 Mar 2009 10:16:07 -0700 |

If the zeros are identifiable from some other information - e.g., hospital costs will be 0 if the patient isn't hospitalized or in this case we would know the visits to a specialist is 0 if the patient is only seen for physical exams, etc. - then a two-part model might work. In this case one uses two models: one for the number of visits if visits are >0 and one (a logistic) for distinguishing 0 vs. non-zero. I have a few papers in Statistics in Medicine in 2001 that may be helpful. I would emphasize that in this case, some of the 0 visits to a specialist are in patients who should have seen a specialist but didn't. Tony Peter A. Lachenbruch Department of Public Health Oregon State University Corvallis, OR 97330 Phone: 541-737-3832 FAX: 541-737-4001 -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Maarten buis Sent: Monday, March 16, 2009 2:08 PM To: stata list Subject: RE: st: Zero-truncated Negative Binomial convergence --- Emily Wilson wrote: > I am having trouble running a zero-truncated negative binomial > regression. The dependent variable is: # of visits to a > specialist physician in the past year, and the distribution is > something like: > 0 visits ~= 93,000 > 1 visit ~= 15,000 > 2 visits ~= 1,000 > 3 visits ~= 500 The zero truncated distribution assumes that there are no zeros. In your case you definately do have zeros. I would start with a regular -poisson-, and than I might worry about excess zeros, for which you can look at the zero inflated poisson (-zip-), the negative binomial (-nbreg-), and zero inflated negative binomial (-zinb-). There is a nice discussion of these models and how to choose between them in this book: http://www.stata-press.com/books/regmodcdvs.html Hope this helps, Maarten ----------------------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://home.fsw.vu.nl/m.buis/ ----------------------------------------- * * 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/ * * 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/

**Follow-Ups**:**R: st: Zero-truncated Negative Binomial convergence***From:*"Carlo Lazzaro" <carlo.lazzaro@tiscalinet.it>

**References**:**RE: st: Zero-truncated Negative Binomial convergence***From:*Maarten buis <maartenbuis@yahoo.co.uk>

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