Glossary // Glossary term Technical
Standardized mean difference (Hedges' g)
An effect size that expresses the difference between two group means in units of their pooled standard deviation, so that studies using different scales can be compared. Cohen's d is the basic form; Hedges' g applies a correction for the slight overestimation of d in small samples. Values depend on which standard deviation is used, and within-subject designs require different formulas, so a g from one design is not automatically comparable with a g from another. How one could reason about recording a catharsis-like change of state: signals, features, inference and context, baselines, self-report, error costs and ethics, and why every step stays uncertain. Nothing on this site measures anyone. Every public claim on this site with its type, evidence level, confidence, sources and review date, and an appraisal of each reference. How claims are graded, how art is kept apart from evidence, and how to report a problem. The works the definition rests on, with the level of evidence each was appraised at. (2013). Calculating and reporting effect sizes to facilitate cumulative science: A practical primer for t-tests and ANOVAs. doi:10.3389/fpsyg.2013.00863 Supports technical statements about Cohen's d, Hedges' g and the different formulas required for within- and between-subject designs. Methods guidance.Where the site uses it
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