Statistics

Effect Size Calculator

Find Cohen's d effect size between two groups.

Calculated Output

Cohen's d 0.6

Formula: d = (mean₁ − mean₂) ÷ pooled SD

Step-by-Step Breakdown

1. Values used:

2. Mean 1 = 78

3. Mean 2 = 72

4. Pooled standard deviation = 10

6. Cohen's d = 0.6

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The math behind it

Cohen's d = (mean difference) ÷ pooled SD. Rough guide: 0.2 small, 0.5 medium, 0.8 large.

Means 78 vs 72, pooled SD 10 → d = 0.6 (medium).

Why report effect size?

A result can be statistically significant yet trivially small; effect size shows practical importance.