[Rasch] Dimensionality & variances

SR Millis srmillis at yahoo.com
Tue Jun 10 06:30:30 EST 2008


I'm fitting a dichotomous Rasch model with 32 items and 873 persons.  My INFITs and OUTFITs range from .76-1.76. However, the PCA of the residuals from that variance explained by the measures was only 28.1. Unexplained variance in 1st contrast was 9.4%.

What might be going on here?

Thanks,
Scott Millis
 

Scott R Millis, PhD, MEd, ABPP (CN,CL,RP), CStat
Professor & Director of Research
Dept of Physical Medicine & Rehabilitation
Wayne State University School of Medicine
261 Mack Blvd
Detroit, MI 48201
Email:  smillis at med.wayne.edu
Tel: 313-993-8085
Fax: 313-966-7682



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