This tool is used to test the null hypothesis that there is no difference between two population means against either one-sided or two-sided alternative hypotheses.
此工具用于检验两个总体平均值之间不存在差异的空值假设，而不是单方或双方的其他假设。
2
The second one is two-sided hypothesis test problem.
第二个是双边假设检验问题。
3
Sometimes the comparison between the drug effects of the two kinds is needed with the mean equivalent of twosided t-test; then the dose of a drug can be gradually extended.