StratumP-value calculator
Enter a test statistic — a z, t, or chi-square value — and get the exact p-value. Everything runs in your browser; nothing is uploaded.
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You have the p. See what is behind it. Stratum runs the test on your own file, reports the effect size beside the p, and lets you click any point to see its row.
Try Stratum freeHow to use it
Pick the distribution your test produced a statistic from, type the value, and choose one- or two-tailed. The p-value updates as you type.
- z (normal) — large-sample tests, proportion tests, a standardized z-score.
- t (Student) — one- and two-sample t-tests and regression coefficients. You'll also need the degrees of freedom (roughly your sample size minus the number of estimated means).
- χ² (chi-square) — tests of independence and goodness of fit. Degrees of freedom come from the table dimensions; chi-square is read in the upper tail, so the "tails" control doesn't apply.
What "two-tailed" means. A two-tailed p-value counts results as extreme in either direction — the usual default when your hypothesis is just "there's a difference." Use one-tailed only when you committed to a direction before seeing the data. For a symmetric z or t, the one-tailed p is exactly half the two-tailed p.
How to read the result
By the common 0.05 convention, p < 0.05 is called statistically significant. But the p-value is only half the story — it tells you whether an effect is probably real, not how big it is. Read the full picture on the p-value glossary page, and always pair it with an effect size and a confidence interval.
Skip the lookup entirely. In Stratum you don't compute the statistic by hand and look up a p-value — load your data and the t-test, ANOVA, correlation, chi-square, and regression all report exact p-values directly, with the matching chart. Download Stratum →
See also
- Other calculators
- Sample-size calculator · Effect-size calculator
- Learn the concept
- What is a p-value? · Confidence interval
- Do it on real data
- Run a t-test