Evidence quality
External validity
The extent to which findings apply to real-world populations and settings.
What it means
Definition
External validity. External validity overlaps with generalisability. A study can be internally rigorous but still poorly matched to routine practice or to the population described in media coverage.
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 tightly controlled specialist-centre trial may not predict outcomes in primary care.