Standard Article

Variance Components

  1. P. J. Solomon

Published Online: 15 JUL 2005

DOI: 10.1002/0470011815.b2a09056

Encyclopedia of Biostatistics

Encyclopedia of Biostatistics

How to Cite

Solomon, P. J. 2005. Variance Components. Encyclopedia of Biostatistics. 4.

Author Information

  1. University of Adelaide, Australia

Publication History

  1. Published Online: 15 JUL 2005


Random variation may have a complex structure, with several identifiable sources and corresponding components of variance. In a hierarchical or multilevel model, parameters may change, for example, between individuals, their variation being measured by variance components. This article reviews the history of the study of variance components and describes methods of estimation. Topics include synthesis of variance, empirical Bayes methods, nonnormal models, and model assessment and prediction.


  • hierarchical;
  • multilevel;
  • nesting;
  • random effects;
  • unbalanced data;
  • estimating equations;
  • REML;
  • synthesis of variance;
  • empirical Bayes;
  • generalized linear models