From test statistic to p-value
Enter your z, t, chi-square, or F statistic and get the exact p-value — one- or two-tailed, with significance verdicts at α = 0.05 and 0.01.
A result this extreme is reasonably likely under the null hypothesis — at the 5% level you would not reject it. Absence of significance is not evidence of absence.
P-values quantify surprise under the null hypothesis — not effect size or importance. Report exact p-values together with effect sizes and confidence intervals.
Frequently asked questions
How do I get the p-value from a t-statistic?
Select t-test, enter the t value and the degrees of freedom (for a one-sample or paired test: n − 1), and choose one- or two-tailed. The calculator returns the exact p-value from the t distribution.
One-tailed or two-tailed — which should I use?
Two-tailed is the default in most fields: it tests for a difference in either direction. Use one-tailed only when your hypothesis specified a direction before you saw the data — and say so in the methods section.
What does p < 0.05 actually mean?
If the null hypothesis were true, data at least as extreme as yours would occur in fewer than 5% of identical studies. It does not mean there is a 95% chance your hypothesis is true, and it says nothing about how large the effect is.
Should I write p = 0.000?
No — p-values are never exactly zero. Report the exact value (p = 0.032) and use p < .001 below that threshold, per APA style.
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