# G*Power is a necessary tool for every researcher's toolkit

## Easy statistical power and sample size calculations

There is an open-source tool available to EVERYONE that allows you to calculate your own

*a priori*and post hoc power analyses. It is called

**G*Power**and as your personal statistical consultant, I highly suggest you go to the following web address and download Version 3.0 to your respective device:

**http://www.gpower.hhu.de/en.html**The researchers that developed this program have made a great contribution to science. It is truly a great and FREE program that can run a litany of different power analyses. You can find out

**in minutes**how large of a sample size that you need, given that you have an idea of the effect size that you are attempting to detect in your study.

Use means, proportions, and variance measures from

**published studies**in your field to have the most empirically rigorous hypothesized effect. Enter these values into G*Power and the adjust the variance and magnitude of the effect size to see how the required sample size changes.

Click on the

**Sample Size**button to access the methods of conducting and interpreting sample size calculations for ten different statistical tests.