MihsabaHow to use
This calculator converts a known test statistic into a p-value. Choose the distribution that belongs to your test: standard normal Z, Student’s t with degrees of freedom, or chi-square with degrees of freedom. Z and t support left-, right- and two-tailed alternatives.
- Choose the distribution used by your test statistic.
- Enter the statistic and degrees of freedom when required.
- Choose the tail from the alternative hypothesis, not from the observed sign.
- Optionally set α and read the p-value.
How it is calculated
Example
Example: with z=1.96 in a two-tailed test, p is about 0.05. A one-tailed test gives roughly half that tail area, which is why the alternative hypothesis should determine the tail before looking at the result.
Important notes
A p-value is not the probability that the null hypothesis is true and does not measure effect size. Its validity depends on the selected distribution, degrees of freedom and assumptions of the original test.
Frequently asked questions
Does p<0.05 mean the effect is practically important?
No. Statistical significance is not effect size or practical importance.
When should I use a two-tailed test?
When the alternative allows a departure in either direction.
Why does t need degrees of freedom?
Because the shape of the t distribution changes with df.
Is chi-square two-tailed here?
No. The chi-square option reports the usual right-tail probability.