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Coefficients Alpha, Beta, Omega, and the glb: Comments on Sijtsma

Published online by Cambridge University Press:  01 January 2025

William Revelle*
Affiliation:
Department of Psychology, Northwestern University
Richard E. Zinbarg
Affiliation:
Department of Psychology, The Family Institute at Northwestern University, Northwestern University
*
Requests for reprints should be sent to William Revelle, Department of Psychology, Northwestern University, Evanston, IL, USA. E-mail: revelle@northwestern.edu

Abstract

There are three fundamental problems in Sijtsma (Psychometrika, 2008): (1) contrary to the name, the glb is not the greatest lower bound of reliability but rather is systematically less than ωt (McDonald, Test theory: A unified treatment, Erlbaum, Hillsdale, 1999), (2) we agree with Sijtsma that when considering how well a test measures one concept, α is not appropriate, but recommend ωt rather than the glb, and (3) the end user needs procedures that are readily available in open source software.

Information

Type
Theory and Methods
Copyright
Copyright © 2008 The Psychometric Society

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