This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
All of the following are analytical epidemiological studies except- 
Select and explain. 
A. Coho study, B. Case - control study, C. Ecological study, D. Field trial
D: Field trial
Answer: D: Field trial 
Explanation: Analytical studies include: Ecological or correlational-with populations as a unit of study Cross-sectional or prevalence-with individuals as a unit of study Case-control or case reference-with individual as a unit of study Coho or followup-with individual as a unit of study (refer pg no:62 park 23rd edition)