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
Best method of variability is - 
Select and explain. 
A. Mean, B. Mode, C. Median, D. Standard deviation
D: Standard deviation
Answer: D: Standard deviation 
Explanation: "Standard deviation is most common and generally most appropriate measure of dispersion (variation)". — Park