单选题
The following sample of 10 items is selected from a populatian. The population variance is unknow.
| 10 | 20 | -8 | 2 | -9 | 5 | 0 | -8 | 3 | 21 |
The standard error of the sample mean is closest to:
【正确答案】
B
【答案解析】
When the populatian variance is unkown, 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,
The standard error of the sample mean is therefore 10.844/100.5 = 3.429≈3.43.