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
Mean and standard deviation can be worked out only if data is on 
Select and explain. 
A. Nominal scale, B. Dichotomous scale, C. Interval/Ratio scale, D. Ordinal scale
C: Interval/Ratio scale
Answer: C: Interval/Ratio scale 
Explanation: Most satisfying scale for measurement of quantities: Metric scale

– Mean and SD can only be worked out on: Interval/Ratio scale

Measurements are east to handle in: Ratio scale.