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Item-analysis data from an experimental study of the effects on item-analysis data of changing item placement and test time limit

Mollenkopf, William G.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
Item Analysis, Power Tests, Test Construction, Test Format, Test Length, Test Speededness, Timed Tests


Item-analysis data are usually obtained from a single test administration, with a given item sequence and time limit. Questions can be raised as to the effects on item data resulting from changes in item position and timing. In this study, two forms of a verbal test and two forms of a mathematics test were used. In each case, both contained the same items, but items coming early in one form were placed late in the other. Each of these forms was administered once with a short time limit and once with generous timing, to comparable groups of high school students. The relationships of various speed and power scores were determined, and the changes which occurred during the added time were studied. Values of the item indices p (proportion right), delta (another difficulty index), and the item-test biserial correlation were obtained for both the speed and the power conditions, and were systematically compared. The proportion right of those attempting the item, the delta index, and the biserial r were all found to have undesirable characteristics for items appearing late in a speeded test.

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