NO.PZ2023061301000027
问题如下：
Which of the following statements is correct regarding the chi-square test of
independence?
选项：
A.The test has a one-sided rejection region.
The null hypothesis is that the two groups are dependent.
If there are two categories, each with three levels or groups, there are six
degrees of freedom.
解释：
A is correct. The test statistic includes squared differences between the observed
and expected values, so the test involves only one side, the right side. B is incorrect
because the null hypothesis is that the groups are independent, and C is
incorrect because with three levels of groups for the two categorical variables,
there are four degrees of freedom.
我知道公式 df=（r-1)(C-1), 可是根据题目， 不是2个categories， 每个categeires 有3个子类目， 所以 row 是2， column 是3吗， 所以算出来是2吗， 为什么解析中说是一个三行三列的表格呢， 谢谢
