Variance components and their implications for statistical information in medical data

E. J. Orav, T. A. Louis, R. H. Palmer, E. A. Wright

Research output: Contribution to journalArticle


We discuss general issues concerning the design and analysis of medical experiments involving repeated measures or hierarchical groupings of subjects within larger study units. Depending on the types of questions being investigated, the correlations induced by clustering can have dramatic impact on the effective sample size. The unique aspects of such experiments must be accounted for during analysis and during interpretation of the results. We illustrate these issues by using a variance components model to investigate the role of leadership in medical practice.

Original languageEnglish (US)
Pages (from-to)599-616
Number of pages18
JournalStatistics in Medicine
Issue number4
StatePublished - Apr 1991
Externally publishedYes


ASJC Scopus subject areas

  • Epidemiology
  • Statistics and Probability

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