“如要检验学生平均每月的饮料消费额是否大于等于60元，每户居民平均固定电话费是否小于等于100元等，此类问题的检验均为单侧检验。”
解答：
另外，
第一次使用ZTEST函数，比较新鲜，补充说明一下。
“For a supplied hypothesized sample mean and a supplied set of values, the Excel Ztest function calculates the one-tailed probability value of the Z-Test.
I.e. the function returns the probability that the supplied hypothesized sample mean is greater than the mean of the supplied data values.
The syntax of the Ztest function is:
ZTEST( array, x, [sigma] )
where the function arguments are:
array-The set of values against which the hypothesized sample mean is to be tested.
x-The hypothesized sample mean.
[sigma]-An optional argument that represents the population standard deviation, if this is known.
If omitted, the calculation uses the sample standard deviation.”
感觉能看懂了，不错！