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From | "Roger B. Newson" <r.newson@imperial.ac.uk> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: Marginsplot after Poisson regression and negative predicted values |
Date | Wed, 08 Jan 2014 10:44:52 +0000 |
Best wishes Roger Roger B Newson BSc MSc DPhil Lecturer in Medical Statistics Respiratory Epidemiology, Occupational Medicine and Public Health Group National Heart and Lung Institute Imperial College London Royal Brompton Campus Room 33, Emmanuel Kaye Building 1B Manresa Road London SW3 6LR UNITED KINGDOM Tel: +44 (0)20 7352 8121 ext 3381 Fax: +44 (0)20 7351 8322 Email: r.newson@imperial.ac.uk Web page: http://www.imperial.ac.uk/nhli/r.newson/ Departmental Web page: http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/ Opinions expressed are those of the author, not of the institution. On 08/01/2014 09:37, Maarten Buis wrote:
I suspect that you mean the confidence interval around the predicted values. It is a known issue with the delta method that is used by -margins- for computing the confidence interval. Generally I would not worry too much about it, as these bounds are failry approximate anyhow, but if you do you can predict the linear predictor with its confidence intervals and transform those to the expected count metric as in <http://www.stata.com/support/faqs/statistics/delta-rule/index.html>. Hope this helps, Maarten On Wed, Jan 8, 2014 at 9:51 AM, James Bernard <jamesstatalist@gmail.com> wrote:Hi all, I have ran a Poisson model. Then tried to run -margins and -marginsplot for one of the variables. The shape of the graph makes sense. But, the range of predicted values of the dependent variable (which is a count variable, obviously) ranges from 1 at its maximum and -6 at its minimum. Is this usual? Am I doing something wrong? Thanks, James * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/