Which study design provides the strongest (most effective) evidence for establishing a cause-and-effect relationship between a treatment and an outcome?

The randomized controlled trial minimizes bias and confounding through randomization and controls, making it the strongest design for demonstrating causation among the options listed.Other options: Case reports have no comparison group. Case-control and cohort studies are observational and more prone to bias and confounding than an RCT.Key exam takeaway: Evidence hierarchy (strongest to weakest among these): RCT > cohort > case-control > case report (systematic reviews of RCTs sit above individual RCTs).