[Rasch] A practical one

John Barnard (EPEC) JohnBarnard at bigpond.com
Mon Oct 10 13:32:34 EST 2005


Dear all

I would appreciate some opinions on the following scenario.

The same paper was given on two occasions. Some 20% of students (let's
call them the repeaters) who sat the first round (and failed) also sat
the second round. In round 1, the repeaters' mean ability is (say) 0.5
logits less than the non-repeaters'. After anchoring the item
difficulties in the first round and using them in round 2 resulted in
the repeaters now doing significantly better (say 0.7 logits on
average). Also the repeaters now have approx the same mean ability as
the non-repeaters in round 2, say 0.8 logits.

The question is this: If the repeaters' mean ability increased by 0.7
logits, how can one account for this (taking the same paper again) to
not unfairly advantage the repeat group in round 2? (I am aware of
learning and other factors, but let's ignore that for the moment.)

Kindly
John 

John J Barnard
Executive Director: EPEC Pty Ltd
www.users.bigpond.com/JohnBarnard/

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