Effect Size Calculator - Cohen's d & eta²
Calculate effect size measures including Cohen's d, eta-squared, omega-squared, and Cramér's V for statistical analysis. Essential for research, psychology, education, and data science to measure practical significance beyond p-values. Supports t-tests, ANOVA, and chi-square tests.
Cohen's d & eta²
d = (M₁ - M₂) / SDpooled, η² = SSbetween / SStotalVariables:
- dCohen's d (effect size)Cohen's d (effect size)
- M₁, M₂Mean of group 1 and 2Mean of group 1 and 2
- SDPooled standard deviationPooled standard deviation
- η²Eta-squared (proportion of variance)Eta-squared (proportion of variance)
How to Use the Effect Size Calculator
- 1
Select Type
Choose Cohen's d or eta-squared (η²).
- 2
Enter Data
Enter means, standard deviations, or sum of squares as required.
- 3
Calculate
Get effect size and interpretation.
Examples
Cohen's d Example
Problem:
M₁=80, M₂=75, SD_pooled=5. Find d.
Solution:
- 1.d = (80 − 75) / 5
- 2.d = 1.0
Result:d = 1.0 (large effect)
The difference between groups is a large effect by Cohen's standards.
Frequently Asked Questions
How do I interpret Cohen's d?
0.2 = small effect, 0.5 = medium, 0.8 = large (Cohen's conventional benchmarks).
Eta-squared vs Cohen's d?
Eta-squared (η²) is for ANOVA (proportion of variance explained). Cohen's d is for t-tests (standardized mean difference).