[Rasch] Linking to compare

Anthony James luckyantonio2003 at yahoo.com
Sun Dec 19 22:32:47 EST 2010

Dear folks
I have developed two versions of the same test. The two tests contain the same items and are only different in one minor non-test factor. I want to compare the characteristics of the items under the two conditions.

Do I need some common items and link the two versions so that I can compare the item difficulties under the two conditions? Can I argue that since both versions contain the same items no linking is required?

Theoretically speaking if we give one test to two groups of persons and run two analyses, the items should have identical measures. Therefore, in my case can I say that any variation in item calibrations is attributed to the condition that I have introduced, without any linking?



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