G*Power is a free statistical calculation utility that provides power analysis functions for multiple hypothesis test families. It offers modules for t tests, F tests, χ² tests, z tests, and several exact tests, with structured input fields for specifying effect size, sample parameters, and significance levels.

G*Power includes calculators for deriving effect size values based on common statistical conventions and allows you to generate numerical tables reflecting variations across selected parameters. The software features graphical displays of power curves and related outputs. This uses a priori, post hoc, sensitivity, and criterion analysis, showing results numerically and visually for interpretation.

Graph your power

G*Power organizes power analysis into categorized menus corresponding to statistical test types. Each test selection displays input panels for selecting tails, distribution assumptions, and effect size parameters. You can compute required sample sizes or determine achieved power by entering values into the parameter fields. The software displays results in structured numeric output tables. These outputs include critical values, noncentrality parameters, and projected power estimates associated with the selected model.

The effect size tools provide built-in formulas for deriving standardized effect values based on common statistical frameworks. These calculators vary depending on the test family selected, such as Cohen’s d for t tests or f² for regression-related F tests. Effect size conventions are displayed alongside entry fields to support consistent parameter selection. Outputs from effect size calculations feed directly into the power analysis panel without requiring external transfer.

It also produces visual representations of power calculations. The graphing module can display power curves across a parameter range, including alpha level or sample size variations. You can adjust axis limits, specify alternative distributions, and generate plots reflecting the assumptions of different statistical approaches. However, it lacks dataset import or direct data analysis features. Numeric summaries and plots can be exported and saved for external interpretation or documentation.

Analyze power

G*Power offers structured power analysis tools for common hypothesis test families. It includes parameter entry panels, effect size computation utilities, numeric result summaries, and plotting features that display power curves. The software focuses on producing power estimates and sample size targets under specified model assumptions. It provides analytical power analysis and visualization, not data analysis. Key features: categorized tests, calculation modules, and outputs.