Statistics and risk
Confidence interval
A range of values that expresses statistical uncertainty around an estimate.
What it means
Definition
Confidence interval. A confidence interval shows the plausible range for an effect estimate given the data and assumptions. Wide intervals suggest imprecision, while intervals crossing a no-effect value can weaken confidence in the result.
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 trial result with a wide confidence interval may be compatible with meaningful benefit, no effect or harm.