Z test calculator
Choose a mean, one-proportion, or two-proportion z test.
How do I use this page?
- Choose the test type.
- Enter the summary data.
- Read z and p.
What this page does not do: The normal approximation requires adequate counts and independent observations.
Further reading
Theory — what is a z test?
A z test standardises the distance between an estimated value and the value assumed under the baseline hypothesis, expressed in standard deviation units. The calculator lets you choose a mean test, a one-proportion test, or a two-proportion test. When comparing two proportions, the standard error uses the pooled proportion from both groups. Unlike the t test, the z test assumes a known population variance rather than estimating it from the sample.
Frequently asked questions
Are z and t tests the same?
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.