All are example for randomised control trials except-
.the major type of randomised controlled trials includes, 1.clinical trials 2.preventive trials. 3.risk factor trials 4.cessation experimnts 5.trial of aetiological agents. 6.evaluation of health services. ref:park&;s textbook,ed 22,pg no 82
Natural experiments
Clinical trials
Risk factor trials
Preventive trials
Epidemiology