NO.PZ2015120604000117
问题如下:
A random sample is 100 CFA candidate's exam scoring. The mean of the scoring is 64. The standard deviation of the population scoring is 15. The distribution is supposed to be normal. The 95% confidence interval for the population mean should be:
选项:
A.61.06 to 66.94.
B.61.06 to 69.94.
C.65.06 to 66.94.
解释:
A is correct.
Because the variance of the population is know and n ≥ 30,so The confidence interval is:
64 ± 1.96(15/10) = 64 ± 2.94 = 61.06 to 66.94.
因为样本方差已知且n>30,我们直接使用置信区间计算:
64 ± 1.96(15/10) = 64 ± 2.94 = 61.06 至 66.94.