P-value

What is p-value?

A p-value is the probability of observing test statistics at least as extreme as the one obtained, assuming the null hypothesis is true. A small p-value (typically below 0.05) is evidence against the null hypothesis. A-Level Maths examines p-values for binomial hypothesis tests and normal hypothesis tests. A p-value alone is not a probability that the null is true — that's a common interpretation slip examiners penalise.