[Rasch] Help with equating partial credit items in pre - post test

Mike Linacre (RMT) rmt at rasch.org
Sun Jun 1 15:07:46 EST 2008

Thank you for your question, Andres.

Ben Wright at www.rasch.org/rmt/rmt101f.htm recommends using pre- and post- 
test data together to estimate the rating scale structure anchors. You can 
then anchor the rating scale structures, and use the post-test data to 
estimate the item anchors.

Rasch measures are remarkably robust against disordered thresholds (low 
frequency categories) so don't collapse categories if they are merely 
sampling effects (not due to structural flaws in the rating scale).

Mike L.

At 5/31/2008, you wrote:
>Which could be the best way to put pre test results on the post test frame 
>of reference?

Mike Linacre
Editor, Rasch Measurement Transactions
rmt at rasch.org www.rasch.org/rmt/ Latest RMT:  21:4 Spring 2008
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