This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Normal Distribution, Skewed Distributions, Subject name: Social & Preventive Medicine
68% values are covered in how many Standard Detions (SD)? 
Select and explain. 
A. 1 SD, B. 2 SD, C. 3 SD, D. 4 SD
A: 1 SD
Answer: A: 1 SD 
Explanation: Normal / Gaussian curve:- Is 'bilaterally symmetrical, bell - shaped'. Mean, Median and Mode coincide. (Mean = Median = Mode) Has mean (u) = 0 and SD (s) = 1. 1) Mean +- 1SD (u +- 1s) covers 68% values. 2) Mean +- 2SD (u +- 2s) covers 95% values. 3) Mean +- 3SD (u +- 2s) covers 99% values.