P-value calculator from F
Choose F, enter the F statistic, numerator df, and denominator df, then keep the right tail for most ANOVA and regression F tests.
Free statistics calculator
P-Value Calculator for Z, T, Chi-Square, and F Tests
Use this free p-value calculator to calculate p-values from z, t, chi-square, and F test statistics. Choose the correct test statistic, tail, degrees of freedom, and alpha level, then get a clear p-value, decision, and interpretation for hypothesis testing homework. Use it for left-tailed, right-tailed, and two-tailed p-value calculations, including t and F test outputs.
- Z p-values Use normal-distribution p-values for z statistics.
- T p-values Use a t statistic and df as a t and p-value calculator.
- Chi-square p-values Use right-tail p-values for common chi-square tests.
- F p-values Use F, df1, and df2 for ANOVA and regression tests.
Calculate a P-Value
Select the statistic from your assignment, formula, calculator, or software output. This page works for p-value from test statistic questions when you know the distribution and required degrees of freedom. The tail choice should match the alternative hypothesis or the test type requested by your instructor.
Use two-tailed for alternatives such as not equal.
Most chi-square tests use a right-tailed p-value.
Most ANOVA and regression F tests use a right-tailed p-value.
Results
Z p-value
Method
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Statistic
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Tail
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Degrees of Freedom
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P-Value
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Alpha
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Decision
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Interpretation
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The p-value depends on the test statistic, distribution, degrees of freedom, and alternative hypothesis. Match the method to your assignment instructions.
Quick Answers for Common P-Value Searches
If you already have a test statistic, the fastest path is to match it to the right distribution, enter the required degrees of freedom, and use the tail from the alternative hypothesis or test type.
T and p-value calculator
Choose T, enter the t statistic and degrees of freedom, then use a two-tailed p-value for a not-equal alternative or a one-tailed p-value for greater/less alternatives.
P-value from test statistic
The statistic alone is not enough. The calculator also needs the distribution, tail direction, and degrees of freedom for t, chi-square, and F tests.
How to calculate a p-value
Convert the test statistic into a tail probability under the null hypothesis, then compare the p-value with alpha to decide whether to reject the null.
What This Calculator Supports
Use this page when you already have the test statistic from a formula, calculator, or software output and need the p-value and conclusion. It is built for common homework workflows where the calculation step is only part of the full hypothesis-test answer.
Z statistic
Calculate left-tailed, right-tailed, or two-tailed p-values from a z statistic.
T statistic
Use this as a t and p-value calculator with a t statistic, degrees of freedom, and the correct tail.
Chi-square statistic
Calculate p-values for chi-square goodness-of-fit and association tests.
F statistic
Calculate a p-value from an F statistic for ANOVA, regression F tests, and variance-ratio checks.
Which P-Value Method Should I Use?
The p-value method should match the distribution of the test statistic. This is why the same statistic value can lead to different p-values under different tests. If your output says F, t, z, or chi-square, choose the matching calculator tab rather than treating every value as a normal z score.
| Statistic | Common use | Typical tail |
|---|---|---|
| Z | Z-tests, normal approximations, and known population SD problems. | Left, right, or two-tailed depending on the alternative. |
| T | T-tests and confidence interval checks when SD is estimated from a sample. | Left, right, or two-tailed depending on the alternative. |
| Chi-square | Goodness-of-fit, independence, association, and variance tests. | Usually right-tailed. |
| F | ANOVA, regression F tests, and variance comparisons using numerator and denominator df. | Usually right-tailed. |
How to Calculate a P-Value Step by Step
A p-value calculation starts with the test statistic and the correct sampling distribution. The calculator does the probability step, but your assignment still needs the setup, assumptions, decision rule, and conclusion.
- Identify the test type: z, t, chi-square, or F.
- Enter the test statistic from your formula or software output.
- Add degrees of freedom for t, chi-square, and F tests.
- Choose left-tailed, right-tailed, or two-tailed based on the alternative hypothesis.
- Compare the p-value with alpha, usually 0.05 unless your assignment says otherwise.
- Write the decision and conclusion in the context of the question, not just the number.
P-Value Examples
These examples show how students usually interpret calculator results after entering a test statistic.
| Example | Calculator setup | How to read it |
|---|---|---|
| Z test | z = 1.96, two-tailed, alpha = 0.05 | The p-value is about 0.05, so the result is right at the common significance cutoff. |
| T test | t = 2.10, df = 24, two-tailed, alpha = 0.05 | Use the t distribution because the standard deviation is estimated from sample data. |
| Chi-square test | chi-square = 10.5, df = 4, right-tailed | Most chi-square tests use the right tail because larger values give stronger evidence against the null. |
| ANOVA or regression F test | F = 4.25, numerator df = 3, denominator df = 28, right-tailed | Use this setup to calculate a p-value from an F statistic; larger F statistics usually mean stronger evidence. |
Calculator Methodology and Validation
This calculator evaluates cumulative probabilities for the normal, Student t, chi-square, and F distributions. One-tailed results use the requested left or right tail. Two-tailed z and t results double the smaller tail probability.
| Validation case | Expected p-value | Purpose |
|---|---|---|
| z = 1.96, two-tailed | about 0.049996 | Checks the standard normal CDF and two-tail handling. |
| t = 2.13, df = 18, right-tailed | about 0.023612 | Checks Student t distribution tail probability. |
| chi-square = 10, df = 5, right-tailed | about 0.075235 | Checks chi-square upper-tail probability. |
| F = 3, df1 = 2, df2 = 20, right-tailed | about 0.072538 | Checks F distribution upper-tail probability. |
Rounding can vary slightly across calculators and software. For graded or research work, compare the final method and rounding with your course instructions or software output.
Common Mistakes to Avoid
- Using a two-tailed p-value when the alternative hypothesis is one-tailed.
- Using a z distribution when the assignment requires a t distribution with degrees of freedom.
- Reading chi-square or F tests as left-tailed tests when the course expects a right-tail p-value.
- Reporting only the p-value without stating the test statistic, degrees of freedom, alpha, and conclusion.
P-Value Calculator FAQs
What is a p-value?
A p-value is the probability, assuming the null hypothesis is true, of getting a test statistic at least as extreme as the observed result.
Should I use a one-tailed or two-tailed p-value?
Use the tail that matches the alternative hypothesis. Use two-tailed when the alternative says the parameter is different, right-tailed when it says greater, and left-tailed when it says less.
Why do chi-square and F tests usually use the right tail?
Chi-square and F test statistics are usually large when the evidence against the null is stronger, so common goodness-of-fit, association, ANOVA, and regression F tests use right-tail p-values.
Does a small p-value prove the alternative hypothesis?
No. A small p-value means the observed result would be unusual under the null hypothesis. The final conclusion should also consider assumptions, study design, effect size, and context.
How do I calculate a p-value from a test statistic?
Choose the matching distribution, enter the test statistic, select the correct tail, and add degrees of freedom when required. Z tests use z, t tests use t and df, chi-square tests use chi-square and df, and F tests use numerator and denominator df.
How do I calculate a p-value from an F statistic?
Choose F, enter the F statistic, add numerator and denominator degrees of freedom, and use the right tail for most ANOVA and regression F tests. The calculator returns the upper-tail probability for that F value.
Can this be used as a t and p-value calculator?
Yes. Choose T, enter the t statistic and degrees of freedom, then select left-tailed, right-tailed, or two-tailed based on the alternative hypothesis.
What information do I need for a p-value calculator from F?
You need the F statistic, numerator degrees of freedom, denominator degrees of freedom, and the tail direction. For standard ANOVA and regression F tests, the tail is usually right-tailed.
Why is my calculator p-value slightly different from software?
Small differences usually come from rounding the test statistic, rounding degrees of freedom, or using a different tail. For assignments, match the method and rounding rules your instructor or software output expects.
What does p-value less than 0.05 mean?
If alpha is 0.05, a p-value less than 0.05 usually means the result is statistically significant and you reject the null hypothesis. The conclusion should still be written in the context of the problem.
Need Help Explaining the P-Value?
A p-value is only part of a hypothesis test. Your assignment may also need the null and alternative hypotheses, test choice, assumptions, alpha decision, effect size, and a conclusion written in context. Statskan can help you understand the calculation and write a responsible explanation that follows your course rules.
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Use Calculators Responsibly
Use this calculator to check p-values, compare software output, and prepare tutoring questions. For graded work, follow your course rules and show the method required.