This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disease Causation, Measurements, Milestones, Subject name: Social & Preventive Medicine
The extent to which a specific health care treatment, service, procedure, program or other intervention does what it is intended to do when used in a community dwelling population is termed its :- 
Select and explain. 
A. Efficacy, B. Effectiveness, C. Effect modification, D. Efficiency
B: Effectiveness
Answer: B: Effectiveness 
Explanation: Effectiveness looks at how the intervention works in real-life settings. Efficacy, tests the same in controlled or laboratory settings. Effect modification is all about stratification & occurs when an exposure has a different effect among different subgroups. Effect modification is associated with the outcome but not exposure.