问题
单项选择题
If a normal distribution has a mean of 10 and a variance of 40, a standardized value of 0.5 corresponds to an observation value that is closest to:（）
A. 6.84.
B. 13.16.
C. 20.00.
答案
参考答案：B
解析：
(x-10)/40×1/2=0.5, x=13.16.