NO.PZ2023061301000006
问题如下：
An analyst suspects that, in the most recent year, excess returns on stocks have
fallen below 5%. She wants to study whether the excess returns are less than 5%.
Designating the population mean as μ, which hypotheses are most appropriate
for her analysis?
选项：
A.
H0: μ = 5% versus Ha: μ ≠ 5%
B.
H0: μ> =5% versus Ha: μ < 5%
C.
H0: μ<= 5% versus Ha: μ > 5%
解释：
B is correct. The null hypothesis is what she wants to reject in favor of the alternative,
which is that population mean excess return is less than 5%. This is a
one-sided (left-side) alternative hypothesis.
为什么不是C呢？她不相信小于等于
