Statistics and risk
Risk ratio
A measure showing how many times more or less likely an outcome is in one group than another.
What it means
Definition
Risk ratio. A risk ratio compares event rates directly. A ratio above 1 suggests higher risk in the exposed or treated group; below 1 suggests lower risk. It should be read with the absolute risk and confidence interval.
What it can tell you
It can show whether a result is being framed as a proportion, percentage or real-world difference.
What it cannot tell you
It cannot show whether the effect is important unless the baseline risk, population and outcome are clear.
Headline trap
Why this matters in headlines
A risk ratio of 2 sounds large, but the practical impact depends on whether the baseline risk was 1 in 10 or 1 in 10,000.