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


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.

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Correspondence to William Revelle.

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Revelle, W., Zinbarg, R.E. Coefficients Alpha, Beta, Omega, and the glb: Comments on Sijtsma. Psychometrika 74, 145 (2009).

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