Distinguish between an observational study and a randomized controlled trial and give a health data example.

Distinguish between an observational study and a randomized controlled trial and give a health data example.

• A. Observational studies observe natural behavior without intervention; RCTs assign participants to interventions randomly; Example: cohort study of smoking on lung cancer; RCT tests a new drug.
• B. Observational studies observe natural behavior without intervention; RCTs assign participants randomly; Example: Cohort study; RCT tests a new drug.
• C. Observational studies are always retrospective; RCTs are always prospective; Example: cross-sectional survey; RCT uses vaccines.
• D. Observational studies assign participants to interventions randomly; RCTs observe natural behavior without intervention; Example: cohort study; RCT tests a new drug.

Answer: (A)