The p-value is the probability of obtaining test results at least as extreme as the results actually observed, under the assumption that the null hypothesis is correct.

What is 'Left-tailed' vs 'Right-tailed'?

Left-tailed: P(X x). Two-tailed: P(|X| > |x|). The choice depends on your alternative hypothesis.

When is a result significant?

Typically, if p-value < significance level (α, usually 0.05), you reject the null hypothesis and say the result is statistically significant.

p-value Calculator

Calculate p-values from Z, t, Chi-Square, and F-statistics.

Test Statistic / Score

Two-Tailed p-value

0

P(|X| > |1.96|)

Left-Tailed P

P(X < 1.96)

Right-Tailed P

P(X > 1.96)

Reference

This calculator uses cumulative distribution functions (CDF) to determine the area under the curve.

Left Tailed

Right Tailed

Two Tailed

Frequently Asked Questions

How to Use

About the p-value

What it calculates

This p-value solves mathematical and statistical problems using standard formulas. Calculate p-value from Z, t, Chi-Square, or F score.

When to use it

Use for homework, data analysis, exam prep, or quick verification of manual calculations.

Example

Adjust the inputs above to model your specific scenario with the p-value.

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Perform one-sample Z-test for known population SD.