This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
If one wants to compare in two characteristics with variable difference, which measurement should be used? 
Select and explain. 
A. Standard deviation, B. Percentile, C. Variance, D. Co-efficient of variation
D: Co-efficient of variation
Answer: D: Co-efficient of variation 
Explanation: None