When I specify an ordinal single level model using MCMCglmm, part of the output includes estimates for the cut points for the response variable scale. Two questions: 1. Is the "post.mean" on the original ordinal scale or do the estimates need to be exponentiated like the coefficients? 2. Why do I occasionally wind up with fewer cut points than the number that existed on the observed variable? Frank Lawrence
MCMCglmm ordinal model
2 messages · Frank Lawrence, Jarrod Hadfield
Hi, The coefficients are on the latent scale, which is the probit scale not log scale. You should end up with one fewer cutpoints than categories because all cutpoints cannot be uniquely estimated with an intercept term in the model. Essentially the first cutpoint is set to 0. See http://permalink.gmane.org/gmane.comp.lang.r.lme4.devel/3644 Cheers, Jarrod Quoting Frank Lawrence <cougar at psu.edu> on Wed, 24 Aug 2011 20:36:09 +0000:
When I specify an ordinal single level model using MCMCglmm, part of the output includes estimates for the cut points for the response variable scale. Two questions: 1. Is the "post.mean" on the original ordinal scale or do the estimates need to be exponentiated like the coefficients? 2. Why do I occasionally wind up with fewer cut points than the number that existed on the observed variable? Frank Lawrence
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