Hedge's g Effect Size Calculator
Quantify the difference between two group means with Hedge's g, a statistical measure of effect size.
Sample Group 1
Sample Group 2
Result: Hedge's g Effect Size
Hedge's g is a measure of effect size, indicating the standardized difference between two means. It is a corrected version of Cohen's d, particularly useful when sample sizes are small and unequal.
Formula: $$ g = \frac{\bar{x}_1 - \bar{x}_2}{S_{pooled}} \times J $$ where $$ S_{pooled} = \sqrt{\frac{(n_1-1)s_1^2 + (n_2-1)s_2^2}{n_1 + n_2 - 2}} $$ and $$ J = 1 - \frac{3}{4(n_1 + n_2 - 2) - 1} $$
Visualization of Means
Visual representation of the sample means on a number line. The positions are relative and for illustrative purposes.
Understanding Hedge's g Effect Size
Hedge's g is used to measure the effect size in studies comparing the means of two groups. It's similar to Cohen's d but includes a correction factor that makes it more suitable for smaller sample sizes, especially when the sizes of the groups are unequal. An effect size quantifies the magnitude of the difference between groups, rather than just indicating if a difference exists (which is what significance tests do).
Interpreting Hedge's g:
- Small effect: g ≈ 0.2
- Medium effect: g ≈ 0.5
- Large effect: g ≈ 0.8
These benchmarks are general guidelines, and the interpretation of effect size can also depend on the context of your research field.
When to Use Hedge's g?
Use Hedge's g when you want to compare the means of two groups and you are concerned about the accuracy of Cohen's d, particularly if you have small or unequal sample sizes. It provides a more accurate estimate of the population effect size in these situations.