Effect Size (Cohen's d) Calculator
StatisticsCalculate Cohen's d to measure the standardized effect size between two group means.
Cohen's d
The standardized difference between the two group means, in units of standard deviation.
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Frequently Asked Questions
What is Cohen's d used for?
Cohen's d quantifies how large the difference is between two group means in a way that is comparable across different studies and measurement scales, unlike a raw mean difference.
How do I interpret the size of Cohen's d?
By Cohen's original convention: around 0.2 is a small effect, 0.5 is a medium effect, and 0.8 or higher is considered a large effect.
How is pooled standard deviation calculated?
Pooled standard deviation combines the variability of both groups into a single weighted estimate. If you only have each group's individual standard deviation, you'll need to compute the pooled value separately before using this calculator.
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