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A Note on "Efficiency of Multiple-Choice Tests as a Function of Spread of Item Difficulties" by Lee J. Cronbach (Psychometrika,1952, 17, 127-147)

Lord, Frederic M.
Publication Year:
Report Number:
ETS Research Memorandum
Document Type:
Page Count:
Subject/Key Words:
Constructed Responses, Cronbach, Lee J., Difficulty Level, Equations (Mathematics), Free Response, Item Analysis, Multiple Choice Tests, Test Items, Test Reliability


A table enlarging Cronbach's Table 1 is presented here to translate Cronbach's delta into some more familiar measure of item discriminating power. It is assumed that all items are free-response items of 50-percent difficulty. An appendix gives the relations among the statistics in the table, according to the assumptions in Cronbach's article for the case where the items are free-response items with different percentages of correct answers and tetrachoric intercorrelations.

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