How to use the P-Value Calculator
- Choose the distribution of your test statistic.
- Enter the statistic and degrees of freedom if needed.
- Pick the tail and significance level, then read the p-value.
What does this tool do?
The p-value is the probability of getting a result at least as extreme as yours if the null hypothesis were true. Small p-values (commonly below 0.05) suggest the data are unlikely under the null.
Use z for large samples or known variance, t for means with estimated variance, chi-square for goodness-of-fit and independence tests, and F for ANOVA and comparing variances.
Why use it?
- Four distributions in one place.
- One- and two-tailed tests.
- Plain-English interpretation.
Accuracy and limits
- Distribution functions are computed numerically to well beyond the 6 decimals shown.
Privacy
The calculation happens instantly in your browser. The numbers you enter are not sent to our servers or saved. There's no account to create and nothing to install.
Frequently asked questions
Does p < 0.05 prove my hypothesis?
No. It means the data would be surprising if the null were true. Effect size and study design matter just as much.
Why are chi-square and F always right-tailed?
Large values of these statistics indicate departure from the null, so the p-value is the area in the right tail.
Last reviewed by the M2Toolkit team.