Comments on: The Exposure Variable in Poisson Regression Models http://www.theanalysisfactor.com/the-exposure-variable-in-poission-regression-models/?utm_source=rss&utm_medium=rss&utm_campaign=the-exposure-variable-in-poission-regression-models Statistical Consulting, Resources, and Statistics Workshops for Researchers in Psychology, Sociology, and other Social and Biological Sciences Mon, 21 May 2012 17:22:58 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Bryan http://www.theanalysisfactor.com/the-exposure-variable-in-poission-regression-models/comment-page-1/#comment-2639 Bryan Fri, 06 Apr 2012 20:15:20 +0000 http://www.theanalysisfactor.com/?p=256#comment-2639 Thanks for your answer. I can express them as rates by dividing the numbers recorded (for example kg of fruit) by the area sampled for each and then taking the log of each and use them as covariates but this still doesn't really reflect the different area sampled for each and how much each subject (fruit transects with different lengths) ought to contribute overall. Do you know of a way to do this in SPSS? Using the GEE scale weight is not an option because that is also only for the dependent variable. Standard 'Weight cases" also wouldn't work because that would weight all the variables and cause problems with the offset. Thanks again for your help, I am really glad that I came across your site and I plan to use you when I need consultation help in the future. Bryan Thanks for your answer.

I can express them as rates by dividing the numbers recorded (for example kg of fruit) by the area sampled for each and then taking the log of each and use them as covariates but this still doesn’t really reflect the different area sampled for each and how much each subject (fruit transects with different lengths) ought to contribute overall. Do you know of a way to do this in SPSS? Using the GEE scale weight is not an option because that is also only for the dependent variable. Standard ‘Weight cases” also wouldn’t work because that would weight all the variables and cause problems with the offset.

Thanks again for your help, I am really glad that I came across your site and I plan to use you when I need consultation help in the future.

Bryan

]]> By: Karen http://www.theanalysisfactor.com/the-exposure-variable-in-poission-regression-models/comment-page-1/#comment-2614 Karen Mon, 02 Apr 2012 14:06:05 +0000 http://www.theanalysisfactor.com/?p=256#comment-2614 Hi Bryan, First, thanks for the kind words. Yes. The offset is really only offsetting the DV. If the IVs are also rates, you'd have to express them in terms of those rates. Best, Karen Hi Bryan,

First, thanks for the kind words.

Yes. The offset is really only offsetting the DV. If the IVs are also rates, you’d have to express them in terms of those rates.

Best,
Karen

]]> By: Bryan http://www.theanalysisfactor.com/the-exposure-variable-in-poission-regression-models/comment-page-1/#comment-2607 Bryan Sat, 31 Mar 2012 20:41:07 +0000 http://www.theanalysisfactor.com/?p=256#comment-2607 Let me start by saying that I think your site is fantastic. When using an offset it appears that it is only applied to the dependent variable, correct? I am curious if the same offset variable used to convert the dependent variable to a rate is also used to scale the independent variables in the model as well or if this must be done in another way. Thanks. Let me start by saying that I think your site is fantastic. When using an offset it appears that it is only applied to the dependent variable, correct? I am curious if the same offset variable used to convert the dependent variable to a rate is also used to scale the independent variables in the model as well or if this must be done in another way. Thanks.

]]> By: Karen http://www.theanalysisfactor.com/the-exposure-variable-in-poission-regression-models/comment-page-1/#comment-2502 Karen Fri, 10 Feb 2012 22:09:17 +0000 http://www.theanalysisfactor.com/?p=256#comment-2502 Thanks, Tarak. Glad I could help! Karen Thanks, Tarak. Glad I could help!

Karen

]]> By: Tarak http://www.theanalysisfactor.com/the-exposure-variable-in-poission-regression-models/comment-page-1/#comment-2498 Tarak Mon, 06 Feb 2012 16:40:49 +0000 http://www.theanalysisfactor.com/?p=256#comment-2498 Thanks so much! After reading this, I better undertand the poisson models that I am running on my data (comparing mortality rates during exposure time intervals vs. non-exposuer time intervals). In medical school, we don't recieve great training on interpreting the stats behind the research we consume. If we don't understand the basic assumptions underlying the stats, I don't know that we can properly interpret anything we read. This is a great contribution! Thanks so much! After reading this, I better undertand the poisson models that I am running on my data (comparing mortality rates during exposure time intervals vs. non-exposuer time intervals). In medical school, we don’t recieve great training on interpreting the stats behind the research we consume. If we don’t understand the basic assumptions underlying the stats, I don’t know that we can properly interpret anything we read. This is a great contribution!

]]> By: » Blog Archive » Modeling Whether or When an Event Occurs: Event History Analysis http://www.theanalysisfactor.com/the-exposure-variable-in-poission-regression-models/comment-page-1/#comment-1298 » Blog Archive » Modeling Whether or When an Event Occurs: Event History Analysis Thu, 13 May 2010 14:03:13 +0000 http://www.theanalysisfactor.com/?p=256#comment-1298 [...] include discrete counts; truncated or censored variables, where part of the distribution is cut off or measured only up to [...] [...] include discrete counts; truncated or censored variables, where part of the distribution is cut off or measured only up to [...]

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