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
The following statistics is used to measure the linear association between two characteristics in the same individuals- 
Select and explain. 
A. Coefficient of variation, B. Coefficient of correlation, C. Chi square, D. Standard error
B: Coefficient of correlation
Answer: B: Coefficient of correlation 
Explanation: .