Statistics and risk
Relative risk reduction
The percentage reduction in risk compared with another group.
What it means
Definition
Relative risk reduction: Relative risk reduction expresses the reduction as a proportion of the original risk. It often sounds more impressive than the absolute risk reduction.
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 fall from 2 in 1,000 to 1 in 1,000 can be called a 50% relative risk reduction, even though the absolute change is 1 in 1,000.