Study design
Case-control study
An observational study comparing people with an outcome to people without it, looking back for exposures.
What it means
Definition
Case-control study. Case-control studies are useful for rare outcomes but can be prone to recall and selection bias. They usually report odds ratios rather than direct risks.
What it can tell you
It can show how close the evidence is to a real human health outcome.
What it cannot tell you
It cannot prove that a treatment works in people unless human outcome data are available.
Headline trap
Why this matters in headlines
A study of a rare cancer may compare affected cases with controls and ask about past exposures.