Statistics and risk
P value
A statistical measure of how compatible the observed data are with a no-effect hypothesis.
What it means
Definition
P value. A p value is not the probability that a claim is true. It indicates how surprising the data would be under a particular null model, and it says little about effect size or clinical importance.
What it can tell you
It can help clarify what sort of evidence or claim is being discussed.
What it cannot tell you
It cannot, by itself, prove that the headline is accurate or clinically important.
Headline trap
Why this matters in headlines
A tiny p value can occur for a trivial effect in a very large dataset.