P-Value Calculator
Converts a test statistic into a p-value.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
two-sided p = 2 × P(T > |t|) chi-square and F: p = P(X > statistic)
Tail areas come from the regularised incomplete gamma and beta functions.
What to watch out for
A p-value is the probability of a result at least this extreme if the null hypothesis were true. It is not the probability that the null hypothesis is true, not the probability that the result is down to chance, and not a measure of how large or important an effect is.
Frequently Asked Questions
What is the p-value for t = 2.228 with 10 degrees of freedom?
0.050012, two-sided. That is why 2.228 is the 5% critical value.
What is the p-value for z = 1.96?
0.049996, two-sided.
What is the threshold for significance?
It is chosen before the study and depends on the field. 5% is common, but it is a convention, and a p-value just over or under it is not much different evidence.