Statistics and risk
Absolute risk reduction
The arithmetic difference in event rates between two groups.
What it means
Definition
Absolute risk reduction. Absolute risk reduction shows how many fewer events occurred in one group compared with another. It is one of the clearest ways to judge the real-world magnitude of a benefit.
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
If events fall from 10% to 8%, the relative reduction is 20%, but the absolute risk reduction is 2 percentage points.