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


  • Afshartous, David
  • Preston, Richard A.


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.

Suggested Citation

  • Afshartous, David & Preston, Richard A., 2010. "Confidence intervals for dependent data: Equating non-overlap with statistical significance," Computational Statistics & Data Analysis, Elsevier, vol. 54(10), pages 2296-2305, October.
  • Handle: RePEc:eee:csdana:v:54:y:2010:i:10:p:2296-2305

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    References listed on IDEAS

    1. Joseph P. Romano & Michael Wolf, 2005. "Stepwise Multiple Testing as Formalized Data Snooping," Econometrica, Econometric Society, vol. 73(4), pages 1237-1282, July.
    2. David Afshartous & Michael Wolf, 2007. "Avoiding 'data snooping' in multilevel and mixed effects models," Journal of the Royal Statistical Society Series A, Royal Statistical Society, vol. 170(4), pages 1035-1059.
    3. Unknown, 2007. "FAPRI U.S Baseline Briefing Book," FAPRI-MU Report Series 44776, Food and Agricultural Policy Research Institute (FAPRI).
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    Cited by:

    1. Tim Goedemé & Karel Van den Bosch & Lina Salanauskaite & Gerlinde Verbist, 2013. "Testing the Statistical Significance of Microsimulation Results: A Plea," International Journal of Microsimulation, International Microsimulation Association, vol. 6(3), pages 50-77.
    2. Tim Goedemé & Tess Penne & Tine Hufkens & Alexandros Karakitsios & Anikó Bernát & Bori Simonovits & Elena Carillo Alvarez & Eleni Kanavitsa & Irene Cussó Parcerisas & Jordi Riera Romaní & Lauri M, 2017. "What Does It Mean To Live on the Poverty Threshold? Lessons From Reference Budgets," Working Papers 1707, Herman Deleeck Centre for Social Policy, University of Antwerp.
    3. Tim Goedemé & Karel Van den Bosch & Lina Salanauskaite & Gerlinde Verbist, 2013. "Testing the Statistical Significance of Microsimulation Results: Often Easier than You Think. A Technical Note," ImPRovE Working Papers 13/10, Herman Deleeck Centre for Social Policy, University of Antwerp.


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