Calculated result
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Standardized mean difference
Cohen’s d divides group 1 minus group 2 mean by the pooled sample standard deviation. Hedges’ g applies J = 1 − 3/[4(n₁+n₂−2)−1] as a small-sample correction.
Worked example
Equal means produce d = 0 and g = 0 when pooled spread is positive.
Interpretation boundary
The sign follows group 1 minus group 2. No universal small, medium, or large label is assigned. This arithmetic does not establish causation, clinical importance, study validity, or treatment effectiveness.