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The Phi Coefficient and Chi Square as Indices of Item Validity

Published online by Cambridge University Press:  01 January 2025

J. P. Guilford
J. P. Guilford*
Affiliation:
University of Southern California
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Abstract

Two new methods of item analysis are described. One involves the computation of the ϕ coefficient (correlation of a fourfold point distribution) and the other involves chi square. The only data required are the proportions of passing individuals in the upper and lower criterion groups, for the determination of ϕ, and in addition, N, for the determination of chi square. Abacs are presented for graphic solution of the two indices of validity, and tests of significance are provided.

Type
Original Paper
Information
Psychometrika , Volume 6 , Issue 1 , February 1941 , pp. 11 - 19
Copyright
Copyright © 1941 Psychometric Society

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Footnotes

*

I am indebted to Mr. H. M. Cox for a critical review of the ideas set forth in this paper.

References

Chesire, L., Saffir, M., and Thurstone, L. L. Computing diagrams for the tetrachoric correlation coefficient, Chicago: Univ. Chicago Bookstore, 1933.Google Scholar
Fisher, R. A. Statistical methods for research workers, Edinburgh: Oliver & Boyd, 1938.Google Scholar