[Rasch] Fwd: Question Concerning Rasch Analysis on Weighted Stage Data

Michael Lamport Commons commons at tiac.net
Thu Jul 14 04:30:04 EST 2011

Here's my question about the Rasch analysis.


We have been trying to measure participants' stages of development via 
surveys that participants to rate their preference for vignettes that 
differ in their order of hierarchical complexity on a 1 to 6 scale.. The 
vignettes are stories which show characters behaving at particular 
stages. My first assumption which I am not sure is an appropriate 
assumption, is that the items of greater difficulty -- higher order of 
hierarchical complexity) will rate. To analyze the data following Bond 
and Fox, we multiplied the response codes (Likert-scale-esque numbers 
1-6) by item orders of hierarchical complexity to attain a weighted 
score. We then run a Rasch analysis on the weighted scores.

Is Rasch analysis appropriate for this form of instrument. The "best" 
one can score on in rating a vignette instrument is 6 on the highest 
order question. But let us say the participant rates 6 on every item, 
even those lower in order of hierarchical complexity and therefore 
difficulty. According to our measurement system, the "best" one can 
score is 6 on every item. Rasch inherently assumes that all items 
measure the same thing, and that their measurement is INDEPENDENT of the 
other items, but this is clearly not the case. Am I wrong, and is Rasch 
appropriate here?

My Best,

Michael Lamport Commons, Ph.D.
Assistant Clinical Professor

Department of Psychiatry
Beth Israel Deaconess Medical Center
Harvard Medical School
234 Huron Avenue
Cambridge, MA 02138-1328

Telephone   (617) 497-5270
Facsimile   (617) 491-5270
Cellular    (617) 320–0896
Commons at tiac.net

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