[Rasch] many facet Rasch model

rsmith.arm at att.net rsmith.arm at att.net
Fri Mar 10 08:17:48 EST 2006

Interesting idea, Randomly Equivalent!  When I learned statistics random assignment ment random not randomly equivalent.  In state testing programs, where test books are randomly assigned, I have seem mean ability differences as high as 0.5 logits across forms.  Hardly equivalent.  Any equating based on the idea that the groups were randomly equivalent is doomed to failure.
Richard M. Smith 
12276 Arbor Lakes Parkway North 
Maple Grove, MN 55369 
voice(w): 763-268-2282 
voice(h): 763-494-5047 

-------------- Original message from "Barth Riley" <barthr at uic.edu>: -------------- 

Hi Susan
What will most likely happen is that Facets will be unable to link ratings of exhibitions across panels. Therefore, it will not be possible to compare an exhibit rated by panel #1 to an exhibit rated by panel #2, etc. If data collection is still ongoing, I would strongly encourage moving raters to multiple panels to ensure a linkage across panels. The alternative strategy is to randomly assign raters to panels. Then we would assume that the panels are “randomly equivalent” and then anchor each panel to a common logit value, typically 0. ‘This group anchoring method can sometimes, though not always, allow disjointed subsets in the data to be connected by Facets. Generally, the more overlap, the better.
Barth Riley, Ph.D.
Res. Asst. Professor & Associate Program Director
Dept. of Disability and Human Development M/C 626
University of Illinois-Chicago
1640 W. Roosevelt Rd.
Chicago, IL 60608
Voice (312) 355-4054
Fax:   (312) 355-4058
Email: barthr at uic.edu
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