Free Effect Size Calculator
Calculate Cohen's d effect size, which measures the standardized difference between two group means.
Cohen's d
0.5432
|d|0.5432
Pooled SD11.0454
Raw Difference6.0000
Cohen's d vs Group 1 Mean
How to Calculate Cohen's d
Formula
d = (Mean1 - Mean2) / Pooled SD
where Pooled SD = sqrt((s1^2 + s2^2) / 2)
Cohen's d expresses the difference between two means in standard deviation units. Guidelines:
Example Calculation
Group 1: mean = 78, SD = 10. Group 2: mean = 72, SD = 12.
- 01Pooled SD = sqrt((100 + 144) / 2) = sqrt(122) = 11.045
- 02d = (78 - 72) / 11.045 = 6 / 11.045 = 0.5432
- 03|d| = 0.5432 which is a medium effect size
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