<prompt> All are example for randomised control trials except -Natural experimentsClinical trialsRisk factor trialsPreventive trials  <response>: Ans. is a i.e., Natural experiments Types of randomized controlled trials Clinical trials 3. Risk factor trials 5. Trial of etiological agents Preventive trials 4. Cessation experiment 6. Evaluation of health services Types of nonrandomized trials. Uncontrolled trials Natural experiments Before and after comparison studies 