This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other Analytical Studies, Subject name: Social & Preventive Medicine
In a study in UK, an association was found between sale of anti-arrhythmic drug and an increase in deaths due to asthma. This is an example of:- 
Select and explain. 
A. Ecological study, B. Coho study, C. Case reference study, D. Experimental study
A: Ecological study
Answer: A: Ecological study 
Explanation: Here we are looking at association between sale of a drug and increase in asthma, with no individual study of consumption of that drug & then getting asthma. Thus, it is Ecological study/ co-relational study. Ecological study is neither forward nor backward study, done at point of time. It can't calculate strength of association/ prevalence. It is based on Secondary data.