【单选题】设 是来自总体 的样本,则样本均值的数学期望和方差为( )。
【单选题】设 是来自总体 的样本, 分别是样本均值和样本方差,则 服从( )分布。
【单选题】设 是来自总体 的样本,则样本均值和样本方差的数学期望分别为( )。
【简答题】第二节:完形填空(共20小题,每小题1.5分,满分30分) 阅读下面短文,掌握其大意,然后从36-55各题所给的四个选项A、B、C和D中,选出可以填入空白处的最佳选项。 When I was ten, my family moved to a housing project in East Los Angeles. Even though we struggled to make 36 mee...
【简答题】阅读理解。 Dear Mom, I'm sorry that I can't go back home for Mother's Day next week. On that day, I'll have to go to an important meeting for my boss, who helps me a lot with my work and life here. But I'l...
【单选题】设总体 , , 和 分别是来自总体 和 的样本且相互独立, 和 分别表示总体 和 的样本均值和样本方差,则下列关于两个正态总体均值的假设检验正确的是( ).
【简答题】Dear Mom, I’m sorry that I can’t go back home for Mother’s Day next week. On that day, I’ll have to go to an important meeting for my boss, who helps me a lot with my work and life here. But I...