[Rasch] Rasch and Misfit

Mike Linacre (RMT) rmt at rasch.org
Sun Jul 6 09:51:44 EST 2008

Agustin asked this important question:
"How can we explain Joe that we cannot provide any measure or score because 
his answers don´t meet the Rasch requirement for fit?"

Fortunately, the situation is rarely that bad. There is almost always a 
reasonable range within which the measure must fall.

Suppose you suspect a candidate of guessing wildly on an MCQ test, so there 
is huge misfit in the response string.
Then there are:
1. The candidate's measure based strictly on the raw score. The lawyers may 
insist on this.
2. The candidate's measure if probable guesses are scored as incorrect. The 
harshest option.
3. The candidate's measure if all "too difficult" items are scored as "not 
administered". The adaptive-test option.
4. (We can imagine more ...)

Surely one of these is suitable to report ....

Mike L.

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