A<unk>  is a type of<unk>  controlled<unk>  in which groups of subjects (as opposed to individual subjects) are<unk> .<unk> s are also known as<unk><unk><unk> s, group-randomised<unk> s, and place-randomized<unk> s.<unk> s are used when there is a strong reason for randomising treatment and control groups over randomising participants.
Cluster randomised controlled trial
Natural history study
Placebo-controlled study
Randomized controlled trial
Multicenter trial
Retrospective cohort study
Prospective cohort study
Nested case–control study