https://www.datanovia.com/en/lessons/t-test-effect-size-using-cohens-d-measure/ Data Mining and Statistics for Decision Support Tue, 27 Jun 2023 23:46:54 +0000 hourly 1 https://wordpress.org/?v=6.8.2 https://www.datanovia.com/en/lessons/t-test-effect-size-using-cohens-d-measure/#comment-28818 Tue, 27 Jun 2023 23:46:54 +0000 https://www.datanovia.com/en/?post_type=dt_lessons&p=11699#comment-28818 Dividing the mean difference by the standard deviation of the differences does not conform with the definition of Cohen’s d. With this computation, if each person in the sample would increase or decrease with the exact same amount (however small or large), then this would yield an effect size of (minus) infinity. The proposed ‘effect size’ says something about the variability of the effect, but nothing about the strength of the effect. To obtain an actual effect size, one should divide the mean difference by the pooled pre- or post-test standard deviation.

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