Power Analysis

Sample Size Calculator

Determine the right sample size for your study. All calculations run locally in your browser.

Sample Size for Means

Compare two group means with a two-sided t-test.

Expected Mean Difference (δ)

The minimum difference you want to detect between groups.

Standard Deviation (σ)

Expected standard deviation of the outcome measure.

Significance Level (α)

Power (1 - β)

Sample Size for Proportions

Compare two proportions with a two-sided z-test.

Proportion 1 (Baseline)

The expected proportion in the control or baseline group.

Proportion 2 (Expected)

The proportion you expect in the treatment group.

Significance Level (α)

Power (1 - β)

Margin of Error Calculator

Calculate the margin of error for a given sample size and confidence level.

Sample Size (n)

Number of respondents or observations.

Confidence Level

Proportion (p)

Use 0.5 for maximum margin of error.