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 f²), given an R² value for a set of independent variables A, and an R² 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 f²), given a value of R².

This calculator will compute the 99%, 95%, and 90% confidence intervals for the f² effect size associated with a multiple regression study, given the f² value, the number of predictors in the model, and the total sample size.

This calculator will compute an R² value for a multiple regression model, given Cohen's f² effect size for the model.