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
Fasting blood sugar (FBS of a population is known to be normally distributed, with a mean of 105 mg%. SD =10. Thus 95% of the population will have FBS within- 
Select and explain. 
A. 104 and 106, B. 95 and 115, C. 85 and 125, D. 75 and 135
C: 85 and 125
Answer: C: 85 and 125 
Explanation: Ref:Parks 23rd edition pg 849. 1SD : confidence limit = 68% 2SD : confidence limit = 95% 3SD : confidence limit = 99.7% 95% means +/- 2SD Here SD =10 So +/- 20 So, between 85 and 125