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A Method for Approximating the Average Intercorrelation Coefficient by Correlating the Parts with the Sum of the Parts

Published online by Cambridge University Press:  01 January 2025

Milton Babitz  and
Noel Keys
Milton Babitz
Affiliation:
University of California
Noel Keys
Affiliation:
University of California
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Abstract

It is noted that the average inter-item correlation, which represents the internal consistency of a test, yields a unique estimate of test reliability. A close approximation to this average is given by a formula which requires the correlation of each item with the total score and the standard deviation of each item. The formula is especially useful in those instances where the number of items is small and where the variation in item sigmas should not be neglected.

Type
Original Paper
Information
Psychometrika , Volume 5 , Issue 4 , December 1940 , pp. 283 - 288
Copyright
Copyright © 1940 The Psychometric Society

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References

* Edgerton, H. A., and Toops, H.A. A formula for finding the average intercorrelation coefficient for unranked raw scores without solving any of the individual intercorrelations. J. Educ. Psychol., 1928, 19, 131-138.

* Babitz, Milton. Measuring student ability in the application of scientific principles. Unpublished seminar study, University of California, 1939.

* Babitz, Milton. Measuring student ability in the application of scientific principles. Unpublished seminar study, University of California, 1939.

† Kuder, G. F. and Richardson, M. W. The theory of the estimation of test reliability. Psychometrika, 1937, 2, 151-160.