G*Power 3 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 power analyses:

• 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 graphic options. It supports both a distribution-based and a design-based input mode.

There is a separate PPC version, as well as a Windows/Vista version. Register for free for info on updates.