44. 5884-!-item-!-187;#058&004663
The arithmetic mean and standard deviation of a certain normal distribution are 13.5 and 1.5, respectively. What value is exactly 2 standard deviations less than the mean?
(A) 10.5
(B) 11.0
(C) 11.5
(D) 12.0
(E) 12.5
Ans:A
請問它問的標準差概念是什麼?