Get access

The statistical recommendations of the American Psychological Association Publication Manual: Effect sizes, confidence intervals, and meta-analysis

Authors

  • Geoff Cumming,

    Corresponding author
    1. School of Psychological Science, La Trobe University, Melbourne, Victoria, Australia
      Geoff Cumming, DPhil, Statistical Cognition Laboratory, School of Psychological Science, La Trobe University, Bundoora, VIC 3086, Australia. Email: g.cumming@latrobe.edu.au
    Search for more papers by this author
    • Geoff Cumming was a member of the APA Publication Manual Revision Working Group for Statistics, but the views expressed in this article are the authors'. This research was supported by the Australian Research Council. We thank Neil Thomason and Eleanor Wertheim for valuable comments on drafts.

  • Fiona Fidler,

    1. School of Psychological Science, La Trobe University, Melbourne, Victoria, Australia
    Search for more papers by this author
  • Pav Kalinowski,

    1. School of Psychological Science, La Trobe University, Melbourne, Victoria, Australia
    Search for more papers by this author
  • Jerry Lai

    1. School of Psychological Science, La Trobe University, Melbourne, Victoria, Australia
    Search for more papers by this author

Geoff Cumming, DPhil, Statistical Cognition Laboratory, School of Psychological Science, La Trobe University, Bundoora, VIC 3086, Australia. Email: g.cumming@latrobe.edu.au

Abstract

Estimation based on effect sizes, confidence intervals, and meta-analysis usually provides a more informative analysis of empirical results than does statistical significance testing, which has long been the conventional choice in psychology. The sixth edition of the American Psychological Association Publication Manual now recommends that psychologists should, wherever possible, use estimation and base their interpretation of research results on point and interval estimates. We outline the Manual's recommendations and suggest how they can be put into practice: adopt an estimation framework, starting with the formulation of research aims as ‘How much?’ or ‘To what extent?’ questions. Calculate from your data effect size estimates and confidence intervals to answer those questions, then interpret. Wherever appropriate, use meta-analysis to integrate evidence over studies. The Manual's recommendations can assist psychologists improve they way they do their statistics and help build a more quantitative and cumulative discipline.

Get access to the full text of this article

Ancillary