# G*Power 3

G*Power 3 is a major extension of, and improvement over, G*Power 2. It covers statistical power analyses for many different statistical tests of the
• F test,
• t test,
• χ2-test and
• z test families and some
• exact tests.
G*Power 3 offers five different types of statistical power analysis:
• A priori (sample size N is computed as a function of power level 1-β, significance level α, and the to-be-detected population effect size)
• Compromise (both α and 1-β are computed as functions of effect size, N, and an error probability ratio q = β/α)
• Criterion (α and the associated decision criterion are computed as a function of 1-β, the effect size, and N)
• Post-hoc (1-β is computed as a function of α, the population effect size, and N)
• Sensitivity (population effect size is computed as a function of α, 1-β, and N)
G*Power 3 provides improved effect size calculators and graphics options. It supports both a distribution-based and a design-based input mode.

G*Power 3 is available for Mac OS X 10.4 and Windows XP/Vista. G*Power 3 is free.

We encourage you to register, that is, to let us know your e-mail address so that we can inform you of updates of the program.

Help, Manual, User Guide

The G*Power 3 User Guide pages at this site (see User guide: Analyses by design  or User guide: Analyses by distribution ) are still mostly empty, and many will remain empty for some time to come. Thus, for the time being, you will have to use G*Power 3 without much additional help. However, some pages have already been completed, which is why you may want to try to find out whether your particular problem is already covered.

There are two more sources that should help you when using G*Power 3:
• A preprint of an article describing G*Power 3 (with examples) available at the Download and register  page
• The previous version, G*Power 2, is still available , although that version of the program is useful only if you still use MS-DOS or Mac OS 7 - 9 on your computer. However, the G*Power 2 manual  may still be helpful for conducting power analyses using G*Power 3.

Samstag, 18. 05. 2013