G*Power is a statistical power analysis program. It is a
major extension of, and improvement over, the previous version,
covering many different statistical tests of the F, t, chi-square, and z
test families as well as some exact tests. G*Power 3 provides improved
effect size calculators and graphics options, it supports both a
distribution-based and a design-based input mode, and it offers five
different types of power analyses. Like its predecessors, G*Power 3 is
free.
Link: G-Power Free Download
