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: Dental
Simplest and most common method to measure variation is: 
Select and explain. 
A. Mean, B. Median, C. SD, D. Range
D: Range
Answer: D: Range 
Explanation: Range: The difference between the smallest and largest value results in a set of data.
Simplest and most common method to measure variation is range.
Reference: Essentials of Preventive and Community Dentistry, Soben Peter, 4th ed page no 395