Confidence intervals for dependent data: Equating non-overlap with statistical significance

David Afshartous, Richard A. Preston

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


We revisit the problem of determining confidence interval widths for the comparison of means. For the independent two-sample (two-sided) case, Goldstein and Healy (1995) draw attention to the fact that comparisons based on 95% error bars are not very effective in assessing the statistical significance of the difference in means and derive the correct confidence interval for such a comparison. We provide an extension to Goldstein and Healy (1995) to account for the correlation structure and unequal variances. We use the results to develop rules of thumb for evaluating differences, in an exploratory manner, like Moses (1987) and Cumming (2009), from the independent case. We illustrate the method for the simple comparison of two means in a real data set, provide R code that may be easily implemented in practice, and discuss the extension of the method to other applied problems.

Original languageEnglish (US)
Pages (from-to)2296-2305
Number of pages10
JournalComputational Statistics and Data Analysis
Issue number10
StatePublished - Oct 1 2010


  • Crossover trial
  • Margin of error
  • Significance test
  • Type I error

ASJC Scopus subject areas

  • Computational Mathematics
  • Computational Theory and Mathematics
  • Statistics and Probability
  • Applied Mathematics


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