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 sopposed 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.
如果这道题给的不是95%,那如何查Z表呢?在Z表中没有找到这个数呢