[Rasch] Interpreting item maps of polytomously scored items

Mike Linacre (RMT) rmt at rasch.org
Thu Aug 24 05:36:04 EST 2006


Tom (and everybody):

The conventional definition of "item difficulty" under a polytomous Rasch 
model is the point on the latent variable at which the highest and lowest 
categories are equally probable. This is usually near the center of  the 
middle category of an odd number of categories, or close to the transition 
between adjacent central categories of an even number of categories.

Mike Linacre.

Tom  Snider-Lotz wrote:
>My question is, what is the best statement to explain the relationship
>between a person and an polytomously-scored item when they are at the
>same spot on the logit scale?
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