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Below you will find descriptions and links to 5 free statistics calculators for computing statistical effect sizes.

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This calculator will tell you the (two-tailed) effect size for a Student t-test (i.e., Cohen's d), given the mean and standard deviation for two independent samples of equal size.

This calculator will tell you the effect size for a hierarchical multiple regression study (Cohen's f^{2}), given an R^{2} value for a set of independent variables A, and an R^{2} value for the sum of A and another set of independent variables B. The value returned by the calculator is the effect size attributable to the addition of set B to the model.

This calculator will tell you the effect size for a multiple regression study (i.e., Cohen's f^{2}), given a value of R^{2}.

This calculator will compute the 99%, 95%, and 90% confidence intervals for the f^{2} effect size associated with a multiple regression study, given the f^{2} value, the number of predictors in the model, and the total sample size.

This calculator will compute an R^{2} value for a multiple regression model, given Cohen's f^{2} effect size for the model.