[R] difference between MASS::polr() and Design::lrm()

From: vito muggeo <vmuggeo_at_dssm.unipa.it>
Date: Mon, 30 Jun 2008 11:38:18 +0200


Dear all,
It appears that MASS::polr() and Design::lrm() return the same point estimates but different st.errs when fitting proportional odds models,

grade<-c(4,4,2,4,3,2,3,1,3,3,2,2,3,3,2,4,2,4,5,2,1,4,1,2,5,3,4,2,2,1) score<-c(525,533,545,582,581,576,572,609,559,543,576,525,574,582,574,471,595,

   557,557,584,599,517,649,584,463,591,488,563,553,549)

library(MASS)
library(Design)

summary(polr(factor(grade)~score))
lrm(factor(grade)~score)

It seems to me that results from lrm() are right..

Am I wrong?
Thanks,
vito

-- 
====================================
Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
UniversitÓ di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 6626240
fax: 091 485726/485612
http://dssm.unipa.it/vmuggeo

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Received on Mon 30 Jun 2008 - 09:41:34 GMT

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