used by people in more than 220 countries!

Below you will find descriptions and links to 4 free statistics calculators for computing sample sizes for different types of studies.

If you like, you may also use the search page to help you find what you need.

This calculator will tell you the minimum sample size required for a hierarchical multiple regression analysis; i.e., the minimum sample size required for a significance test of the addition of a set of independent variables B to the model, over and above another set of independent variables A. The value returned by the calculator is the minimum sample size required to detect an effect of the specified size, probability level, and power level for the addition of set B to the model.

This calculator will tell you the minimum required sample size for a multiple regression study, given the desired probability level, the number of predictors in the model, the anticipated effect size, and the desired statistical power level.

This calculator will compute the sample size required for a study that uses a structural equation model (SEM), given the number of observed and latent variables in the model, the anticipated effect size, and the desired probability and statistical power levels. The calculator will return both the minimum sample size required to detect the specified effect, and the minimum sample size required given the structural complexity of the model.

This calculator will tell you the minimum required total sample size and per-group sample size for a one-tailed or two-tailed t-test study, given the probability level, the anticipated effect size, and the desired statistical power level.