, 74:145

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

Theory and Methods

DOI: 10.1007/s11336-008-9102-z

Cite this article as:
Revelle, W. & Zinbarg, R.E. Psychometrika (2009) 74: 145. doi:10.1007/s11336-008-9102-z


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.


reliability internal consistency homogeneity test theory coefficient alpha coefficient omega coefficient beta 

Copyright information

© The Psychometric Society 2008

Authors and Affiliations

  1. 1.Department of PsychologyNorthwestern UniversityEvanstonUSA
  2. 2.Department of Psychology, The Family Institute at Northwestern UniversityNorthwestern UniversityEvanstonUSA

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