Statistical power calculator
Plan two equally sized independent groups using a normal approximation.
How do I use this page?
- Choose the unknown quantity.
- Enter effect, alpha and power or n.
- Record the assumptions with the result.
What this page does not do: This is a planning approximation. The exact design may require adjustments for the test, sampling scheme and missing data.
Further reading
Theory — what is a statistical power calculator?
A statistical power calculator helps plan a study with two equally sized, independent groups using a normal approximation. Power is the probability of rejecting the baseline hypothesis when the assumed effect truly exists in the population. Increasing sample size, with other factors held constant, raises test power, but it cannot fix a flawed study design or biased measurement. The tool helps estimate the required sample size before collecting data.
Frequently asked questions
Does a larger sample always increase power?
See also
A/B test calculator
Compare two proportions in an A/B test. Calculate conversion rates, difference, uplift, z score, p value and c
A/B test planning — sample size, MDE and duration
Plan a two-proportion experiment, estimate detectable effect and traffic duration.
ACF and PACF autocorrelation calculator
Calculate ACF and PACF across time-series lags. Review the chart, reference bounds and coefficient table.