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Before you conduct your experiment, determine the sample size needed to detect meaningful effects without wasting resources. Do you intend to perform tests of means, variances, proportions, or correlations? Do you plan to fit a one-way, two-way, or repeated-measures ANOVA model? Do you want to fit a Cox proportional-hazards model or compare survivor functions using a log-rank test? Use Stata's power commands or interactive Control Panel to compute power and sample size, create customized tables, and automatically graph the relationships between power, sample size, and effect size for your planned study. And much more.

Learn about power and sample-size analysis.
Watch A tour of power and sample size.
Watch additional Power and sample-size features.
Classic comparisons

• Means (t-tests)
• Proportions
• Variances
• Correlations
• McNemar's test
• Clustered data

• One-way models
• Two-way models
• Repeated-measures models

• Slope test
• Coefficient-of-determination test
• Partial-correlation test

• Cochran—Mantel—Haenszel test
• Matched case—control studies
• Cochran—Armitage trend test

• One-sample mean
• Two-sample means
• One-sample proportion
• Two-sample proportions
• Log-rank test

• Log-rank test of survival functions
• Cox proportional hazards model
• Exponential regression
• Clustered data

Solve for

• Power
• Sample size
• Number of clusters
• Cluster size
• Effect size (minimum detectable effect)

Specify lists of

• Alpha values
• Power levels
• Beta values
• Sample sizes
• Ratios of sample sizes
• And more

Multiple scenarios using

• All combinations of values
• Parallel lists of values

Control panel interface

• Select analysis type from descriptive summaries
• Specify list of power, sample size, or other levels
• Automated tables and graphs
• Customize tables and graphs
• Command interface too (of course)

• Matched case–control studies
• Cohort studies
• Cross-sectional studies
• Balanced
• Unbalanced
• Cluster randomized designs

Tables

Graphs

• Automated
• Customized
• Simple or comparative

Save results to dataset

Additional resources

• Power, Precision, and Sample-Size Reference Manual
• An Introduction to Stata for Health Researchers, Fifth Edition by Svend Juul and Morten Frydenberg
• The Stata Blog: Calculating power using Monte Carlo simulations: The basics
• The Stata Blog: Calculating power using Monte Carlo simulations: Running your simulation using power
• The Stata Blog: Calculating power using Monte Carlo simulations: Linear and logistic regression
• The Stata Blog: Calculating power using Monte Carlo simulations: Multilevel/longitudinal models
• The Stata Blog: Calculating power using Monte Carlo simulations: Structural equation models
• Power, precision, and sample-size analysis flyer

Also see precision and sample-size analysis for confidence intervals and group sequential designs.

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