P-Value Calculator
Calculate one-tailed and two-tailed p-values from Z, T, or Chi-square statistics.
P-Value Results
About the P-Value Calculator
What is a P-Value?
A p-value measures the probability of obtaining test results at least as extreme as the observed results, assuming the null hypothesis is true. Smaller p-values indicate stronger evidence against the null hypothesis.
How to Use
Enter your test statistic, select the test type, and provide degrees of freedom for T and Chi-square tests. The calculator returns one-tailed and two-tailed p-values with significance interpretation.
What is the difference between one-tailed and two-tailed p-values?
A one-tailed test looks for an effect in one direction only. A two-tailed test looks for an effect in either direction and is generally twice the one-tailed value for symmetric distributions.
What does it mean if p < 0.05?
By convention, if the p-value is less than 0.05, the result is considered statistically significant, meaning there is less than a 5% probability the observed result occurred by random chance.
Do I need degrees of freedom for a Z-test?
No. The standard normal (Z) distribution does not depend on degrees of freedom. Only T and Chi-square tests require degrees of freedom.
Is this calculator free?
Yes, BestCalc's p-value calculator is completely free with no ads or registration required.