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st: RE: nonsense category in ordered logit


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: nonsense category in ordered logit
Date   Mon, 21 Feb 2005 20:41:59 -0000

By showing that -logit- with two and -ologit- 
with three give essentially equivalent results? 

Nick 
n.j.cox@durham.ac.uk 

E. Michael Foster

> 	I have data on an ordered outcome coded from 1 to 3.  
> Suppose I suspect 
> that the distinction between levels 2 and 3 is 
> meaningless--i.e., nothing 
> substantive would be lost if I just recoded the 3s to 2s.
> 
>         One implication would be that the proportional odds 
> assumption 
> wouldn't not hold for the 3-category model because the 
> difference between 
> levels 2 and 3 has nothing to do with the X variables.
> 
>          I could test this, but it seems like a weak test.  The 
> proportional odds assumption could be violated for any of 
> several reasons.
> 
> 	How do I demonstrate to my psychologist colleagues (the 
> measure is a psych 
> measure) that collapsing 3 categories into 2 is harmless?

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