Power and sample size

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Power and sample size

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

ANOVA

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

Linear regression

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

Watch Power analysis for cluster randomized designs and linear regression.

Contingency tables

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

Cluster randomized designs

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

Watch Power analysis for cluster randomized designs and linear regression.

Survival analysis

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)

Designs

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

Tables

Automated
Customized

Graphs

Automated
Customized
Simple or comparative

Save results to dataset

Add your own methods

Additional resources

Watch Power and sample size tutorials

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

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