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
Confidence limit is calculated by using 
Select and explain. 
A. Mean and standard error, B. Mean and standard deviation, C. Median and standard deviation, D. Median
B: Mean and standard deviation
Answer: B: Mean and standard deviation 
Explanation: None