NO.PZ2022123001000107
问题如下：
Consider a two-tailed test of the hypothesis that the population mean is zero. The sample has 50 observations. The population is normally distributed with a known variance.
At a 0.05 significance level, the rejection points are most likely at:
选项：
A.–2.010 and 2.010 B.–2.009 and 2.009 C.–1.960 and 1.960解释：
The appropriate test statistic is a z-statistic because the sample comes from a normal distributed population with known variance. A z-test does not use degrees of freedom. This test is two-sided at the 0.05 significance level, and the rejection point conditions are z > 1.960 and z < –1.960.
df=50-1=49，
two tailed- a/2
然后得出答案A，错在哪里了呢？
