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st: problems with ztnb and ztp

From   Gillian Holloway <>
Subject   st: problems with ztnb and ztp
Date   Thu, 13 Mar 2008 11:30:53 -0600

Hi Statalisters,

I'm analyzing zero-truncated bird count data using the standard code for zero-truncated poisson and zero-truncated negative binomial regression. However, when I calculate the predicted values I'm getting some estimates below 1, even though 1 is the minimum observed value in the data. Any ideas what the problem could be?

Example code:

ztp Count SLSoft if Count>0 & Sppcode==38, iterate(100)
predict GRJA

Thanks, Gillian

Alberta Biodiversity Monitoring Institute
Department of Biological Sciences
CW 405, Biological Sciences Centre
University of Alberta

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