NO.PZ2017092702000138
问题如下：
For a small sample with unknown variance, which of the following tests of a hypothesis concerning the population mean is most appropriate?
选项：
A.
A t-test if the population is normally distributed
B.
A t-test if the population is non-normally distributed
C.
A z-test regardless of the normality of the population distribution
解释：
A is correct.
A t-test is used if the sample is small and drawn from a normally or approximately normally distributed population.
方差已知用Z，方差未知用t，非正态总体且小样本不可估计
正态分布与Z分布和T分布都关系是什么呢？Z分布是正态分布的简称吗？T分布一定会正态分布吗？
