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Test Reliability and Correction for Attenuation

Published online by Cambridge University Press:  01 January 2025

Helmer G. Johnson
Helmer G. Johnson*
Affiliation:
University of Minnesota
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Abstract

Evidence is cited to show that specificity, or lack of equivalence, in the comparable forms of tests has a tendency to lower the value of reliability coefficients but has no tendency to lower the value of observed trait coefficients. This implies that the greater the lack of equivalence, the higher will be coefficients corrected for attenuation. Errors of measurement are supposed to reduce the magnitude of observed trait coefficients. Since specificity does not lower the correlation between two tests and since the split-half and equivalent-form reliability coefficients treat specificity as error, it follows that these two coefficients cannot legitimately be used in Spearman's correction-for-attenuation formula.

Type
Original Paper
Information
Psychometrika , Volume 15 , Issue 2 , June 1950 , pp. 115 - 119
Copyright
Copyright © 1950 Psychometric Society

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