**Instructions:** This effect size calculator for the t-statistic allows you to compute the value of \(r^2\) (r-squared) if you know the t-statistic (\(t\)) and the number of degrees of freedom (\(df\)):

## More About the Effect Size for the T-Statistic

The idea of the effect size is to measure the size of an effect, without getting inflated by the sample size(s), which happens with the traditional use of the p-value in hypothesis testing. One measure of the size of the effect is \(r^2\) (r-squared), which is computed as

\[ r^2 = \frac{t^2}{t^2+df} \]The value of \(r^2\) is interpreted as the proportion of variation in the dependent variable that is explained by the independent variable