问题如下：
Using the Excel function NORM.S.DIST or a normal prob-ability table, what are the critical values when testing the null hypothesis, , against
a. a one-sided lower alternative using a size of 10%?
b. a one-sided upper alternative using a size of 20%?
c. a two-sided alternative using a size of 2%?
d. a two-sided alternative using a size of .1%?
选项：
解释：
a. The lower-tailed critical value is -1.28.
b. The one-sided upper-critical value is 0.84.
c. A two-sided alternative with a size of 2% uses the same critical value as a one-sided upper test, which is 2.32. Each tail has probability 1% when using the critical value.
d. This size corresponds to the same critical value as a .05% upper-tailed test, which is 3.29.
原假设是等号，为啥会有单边得出现。
