Free interactive student tool
Free Effect Size Calculator
Free Effect Size Calculator. Cohen's d, r, eta-squared and chi-square effect sizes with interpretation cautions.
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Standardized mean difference
How this tool reaches its result
Cohen’s d divides a mean difference by the pooled within-group standard deviation; Hedges’ g applies a small-sample correction.
Standardized mean difference
Worked context
How to interpret the output
A ten-point difference with a pooled SD of twenty gives d = 0.50.
Important limitation
What the result cannot decide for you
Interpret magnitude in the discipline and outcome context rather than relying only on generic labels.