Item analysis techniques commonly assume that item difficulties are stable over varying test contexts. The current emphasis on information-efficiency and individualized selection of items has made context stability a critical assumption. The simple item difficulties and Rasch log easiness values of 15 verbal analogy items were compared over seven internally consistent analogy tests. The results indicate that 60% of the items varied over contexts and that context difficulty was a factor for 27% of the items. The general applicability of item-parameter-invariant models is questioned by the finding of contextual interaction for parameter estimates.
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