单选题
The following sample of 10 items is selected from a population. The population variance is unknown.
| 10 | 20 | -8 | 2 | -9 | 5 | 0 | -8 | 2 | 3 |
The standard error of the sample mean is closest to:
【正确答案】
A
【答案解析】
A is correct. When the population variance is unknown, the standard error of the sample mean is calculated as
where s is the sample standard deviation and n is the size of the sample.
The sample standard deviation is
In this problem,
