问题
单项选择题
Given that the variance is 289 for a random sample of 500 stocks. Find out the standard error of the sample mean is closest to:（）
A.0.67.
B. 0.76.
C. 0.99.
答案
参考答案：B
解析：
The standard error of the sample mean is s/n1/2=2891/2/5001/2=0.76