Statistics & probability
Independent-samples effect size
Compare two sample means in pooled standard-deviation units.
A clear answer. Here’s how.
Cohen’s d=(mean₁−mean₂)/pooled sample SD, with pooled variance weighted by n−1. Also reports Hedges’ g using the exact gamma-function small-sample correction J(df). Requires two independent samples of at least two values and positive pooled variance. This pooled-standardiser definition assumes a common variance scale; no universal small/medium/large judgement is applied.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- First sample
- 10, 12, 9, 11, 13
- Second sample
- 8, 9, 11, 7, 10
Example result
- Cohen’s d (first − second)
- 1.26491106407
- Hedges’ g
- 1.14183943434
- Pooled sample standard deviation
- 1.58113883008
- Degrees of freedom
- 8