问题如下：
When evaluating mean differences between two dependent samples, the most appropriate test is a:
选项：
A.chi-square test.
B.paired comparisons test.
C.z-test.
解释：
B is correct.
A paired comparisons test is appropriate to test the mean differences of two samples believed to be dependent.
为什么选B? ..我很有疑问啊！因为在讲课视频里面说 检验两个总体分：相互独立和不是相互独立，sample not independent ，paired comparison test 。 这道理说了 independent ，相互独立了， 为什么还是选B
