Study design

Study design decides what a piece of research is entitled to claim. A randomised trial can support a statement about cause; a cohort study is better suited to frequency, long-term safety and how a treatment behaves outside trial conditions; a case report describes one person and settles nothing on its own.

We report design because the design is usually where the interesting part of a health story is. A finding that sounds decisive in a press release often rests on a design that could not have produced a decisive answer.