问题如下：
In the step "stating a decision rule" in testing a hypothesis, which of the following elements must be specified?
选项：
A.Critical value
B.Power of a test
C.Value of a test statistic
解释：
A is correct.
The critical value in a decision rule is the rejection point for the test. It is the point with which the test statistic is compared to determine whether to reject the null hypothesis, which is part of the fourth step in hypothesis testing.
请问Power of a test是什么东西？
还有请问stating a decision rule是什么意思？
