- 搜标题
- 搜题干
- 搜选项
单项选择题
They sang songs to amuse themselves during the break.
They sang songs to amuse themselves during the break.
A、become
B、treat
C、entertain
D、recreate
是来自正态总体
的样本，且
已知，
是样本均值，
是样本标准差，则检验假设
，
所用的统计量是
