system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
To test the association between risk factors and disease, which of the following is the weakest study design?
assistant
The correct answer is  Ecological studies, as they donot take into consideration individual data of exposure & diseases, have poorest evidence of determining association. Hence they are considered as weak studies. These are done at point of time & commonly used in nutritional surveys. Order from strong to weak study determining association:Randomized Control Trial > Retrospective Coho Study > Prospective Coho Study > Case control study > Cross sectional study > Ecological study.