NO.PZ2017092702000113
问题如下:
For a sample size of 17, with a mean of 116.23 and a variance of 245.55, the width of a 90% confidence interval using the appropriate t-distribution is closest to:
选项:
A.13.23.
B.13.27.
C.13.68.
解释:
B is correct.
The confidence interval is calculated using the following equation: Sample standard deviation (s) = = 15.670. For a sample size of 17, degrees of freedom equal 16, so t0.05 = 1.746. The confidence interval is calculated as
Therefore, the interval spans 109.5943 to 122.8656, meaning its width is equal to approximately 13.271. (This interval can be alternatively calculated as 6.6357 × 2).
在查表或做题的时候,怎么判别是单尾还是双尾呢?比如说这题,90%的level查表的时候就要查0.05(不是太懂),谢谢!