, 74:145 | Cite as

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

  • William Revelle
  • Richard E. Zinbarg
Theory and Methods


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 ω t (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 ω t 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 


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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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