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
A person wants to study a disease &;x&; and fat consumption. He obtained data for number of people affected with &;x&; from the government and the details of fat consumption from food industry. Type of study is 
Select and explain. 
A. Ecological study, B. Cross sectional study, C. Pesiological study, D. Experimental study
A: Ecological study
Answer: A: Ecological study 
Explanation: Ecological (correlations) study. Unit of study is population (results not applicable to individuals). Done in a small time frame. It is inferior to coho and case control. Reference: Park's textbook of preventive and social medicine,K.Park,21st edition,page no:59 & 22nd edition, pg no.60.