P-Value Calculator
Calculate the exact p-value from Z, t, Chi-square, or F test statistics.
What is a P-Value?
The p-value (probability value) is the probability of obtaining test results at least as extreme as the observed results, assuming that the null hypothesis (H₀) is true. It is a fundamental concept in hypothesis testing and statistical inference.
A small p-value (typically ≤ 0.05) indicates strong evidence against the null hypothesis, suggesting that the observed effect is statistically significant. A large p-value suggests that the data is consistent with the null hypothesis.
How to Interpret the P-Value
Supported Tests
Z-Test (Normal)
For large samples (n ≥ 30) when population variance is known.
Student's T-Test
For small samples or unknown population variance. Requires degrees of freedom.
Chi-Square Test (χ²)
For categorical data analysis and goodness-of-fit tests.
F-Test (Fisher)
For ANOVA and comparing variances. Requires numerator/denominator df.
Important Notes
- •This calculator uses mathematically exact algorithms (regularized incomplete beta and gamma functions) for accurate results matching SPSS and R output.
- •Statistical significance alone does not imply practical importance. Always consider effect sizes and confidence intervals.
- •For comprehensive statistical analysis, we recommend using our professional consulting services or software like SPSS, R, or Python.