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Kappa and Its Dependence on Marginal Rates

  1. Richard J. Cook

Published Online: 15 JUL 2005

DOI: 10.1002/0470011815.b2a04024

Encyclopedia of Biostatistics

Encyclopedia of Biostatistics

How to Cite

Cook, R. J. 2005. Kappa and Its Dependence on Marginal Rates. Encyclopedia of Biostatistics. 4.

Author Information

  1. University of Waterloo, Waterloo, Ontario, Canada

Publication History

  1. Published Online: 15 JUL 2005

Abstract

The kappa statistic is a widely used measure for quantifying agreement between raters using nominal scales. It is advocated on the grounds that it “corrects” for a level of agreement that would be expected by chance alone based on the marginal rates. The operating characteristics of kappa, however, show that it responds in a complicated and unintuitive way to subject-specific and marginal agreement. Modifications to kappa and supplementary statistics, which have been proposed to help interpret kappa are discussed. Remarks are made as to why the kappa statistic has such problematic features.

Keywords:

  • agreement;
  • association;
  • contingency table;
  • kappa;
  • margins;
  • reliability