How it works
Cohen’s d = difference of means divided by pooled sample SD; pooled variance weights each sample variance by n−1.
Input definitions
- First mean
- Enter the value in the labeled unit.
- First sample standard deviation
- Enter the value in the labeled unit.
- First sample size
- Enter the value in the labeled unit.
- Second mean
- Enter the value in the labeled unit.
- Second sample standard deviation
- Enter the value in the labeled unit.
- Second sample size
- Enter the value in the labeled unit.
A worked example
- First mean
- 12
- First sample standard deviation
- 2
- First sample size
- 20
- Second mean
- 10
- Second sample standard deviation
- 2
- Second sample size
- 20
Assumptions & limits
Uses the units and scope stated in the input labels. Results are rounded for display; verify the model is appropriate for your situation.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-18. Content checked against the stated method and examples. Our verification approach.
Common questions
Does this calculate a significance test?
No. This is an effect-size estimate under pooled-SD assumptions. It does not supply a p-value, confidence interval or small-sample Hedges correction.
How does Cohen’s d for independent samples work?
Cohen’s d = difference of means divided by pooled sample SD; pooled variance weights each sample variance by n−1.
What should I check before using Cohen’s d for independent samples?
Uses the units and scope stated in the input labels. Results are rounded for display; verify the model is appropriate for your situation.