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The Maximum Expected Correlation Between Two Multiple-Choice Tests

Published online by Cambridge University Press:  01 January 2025

Paul Horst*
Affiliation:
University of Washington

Abstract

A formula is derived which gives the maximum expected correlation between two multiple-choice tests as a function of the distributions of proportions correct for the items in the two tests and the probability of chance success. The formula is similar to one derived by Carroll based on “true” item difficulties. A numerical example is provided.

Type
Original Paper
Copyright
Copyright © 1954 The Psychometric Society

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References

Carroll, J. B. The effect of difficulty and chance success on correlations between items or between tests. Psychometrika, 1945, 10, 119CrossRefGoogle Scholar
Ferguson, G. A. The factorial interpretation of test difficulty. Psychometrika, 1941, 6, 323329CrossRefGoogle Scholar
Plumlee, L. B. The effect of difficulty and chance success on item-test correlation and on test reliability. Psychometrika, 1952, 17, 6986CrossRefGoogle Scholar