G*Power (Erdfelder, Faul, & Buchner, 1996) was designed as a general stand-alone power
analysis program for statistical tests commonly used in social and behavioral research.
G*Power 3 is a major extension of, and improvement over, the previous versions. It
runs on widely used computer platforms (i.e., Windows XP, Windows Vista, and Mac OS
X 10.4) and covers many different statistical tests of the t, F, and chi2 test families.
In addition, it includes power analyses for z tests and some exact tests. G*Power
3 provides improved effect size calculators and graphic options, supports both distribution-based
and design-based input modes, and offers all types of power analyses in which users
might be interested. Like its predecessors, G*Power 3 is free.