This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
Whch of the following us used to compare two data sets taken on two different scales of measurement? 
Select and explain. 
A. Coefficient of variation, B. Standard detion, C. Standard error, D. Variance
A: Coefficient of variation
Answer: A: Coefficient of variation 
Explanation: .