How to report effect size

By some counts there are more than 70 effect size indexes. Some of them you will be familiar with (e.g., odds ratio, relative risk). Some double-up as test statistics (e.g., r, R2). While others sound like planets from Star Trek (e.g., the Pillai-Bartlett V).

Most effect size indexes can be grouped into one of two families:

  1. differences between groups, a.k.a the d family (e.g., risk difference, risk ratio, odds ratio, Cohen’s d, Glass’s delta, Hedges’ g, the probability of superiority)
  2. measures of association, a.k.a. the r family (e.g., the correlation coefficient r, R2, Spearman’s rho, Kendall’s tau, phi coefficient, Cramer’s V, Cohen’s f, η2)

For more, see my book Effect Size Matters:

One thought on “How to report effect size

  1. Dr. William Johnson October 21, 2022 / 11:20 am

    Dr. Ellis’ books are great resources for those teaching and publishing.

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