在统计学的实际运用中,常常需要强调一类假设为应当或期望实现的假设,它是()
A.零假设
B.虚无假设
C.备择假设
D.对立假设
参考答案:C
When I was a very young children,my father created a regular practice I remember well years late.Every time he arrived home at end of the day ,we’d greet het at the door.He would ask who we was and pretend not to knowing us,Then he and my mother would have had a drink while she prepared dinner and they would talk about his day and hers.While they chat,my father would lift my sister and me up to sit in the top of the fridge.It was both excited and frightening to be up there!
My sister and I thought he was so cool for putting us there.
4()
如图,从同一高度以相同的速率分别抛出质量相等的三个小球,一个竖直上抛,一个竖直下抛,另一个平抛,则它们从抛出到落地过程中
A.运行的时间相等
B.落地时的机械能不同
C.落地时的速度相同
D.在空中任意时刻三个物体的机械能相同