NO.PZ2017092702000124
问题如下：
Which of the following statements regarding a one-tailed hypothesis test is correct?
选项：
A. The rejection region increases in size as the level of significance becomes smaller.
B. A one-tailed test more strongly reflects the beliefs of the researcher than a two tailed test.
C. The absolute value of the rejection point is larger than that of a two-tailed test at the same level of significance.
解释：
B is correct.
One-tailed tests in which the alternative is "greater than" or "less than" represent the beliefs of the researcher more firmly than a "not equal to" alternative hypothesis
一个双尾检验是例如均值是否等于0，此时检验结果无论是远大于0还是远小于0都可以拒绝原假设。并没有一个明确的方向。
而一个单尾检验有确定的方向，例如检验均值是否大于0。此时只有均值远小于0才可以拒绝原假设。
所以单尾的检验更有针对性，反应出来检验者对于检验的方向和信心更强。
双尾要除以2，比单尾小啊
