【单选题】设随机变量 X 与Y 的方差存在且不等于 0 ,则D(X+Y)=D(X)+D(Y) 是X 与Y( ).
【简答题】设随机变量X和Y的方差存在且不等于0,则D(X+Y)=D(X)+D(Y)是X和Y[ ] (A) 不相关的充分条件,但不是必要条件; (B) 独立的必要条件,但不是充分条件; (C) 不相关的充分必要条件; (D) 独立的充分必要条件.
【单选题】设随机变量X和Y的方差存在且不等于0,则D(X+Y)=D(X)+D(Y)是X和Y
【单选题】听力原文:M: I am just writing Mary about our vacation. Why don't you enclose this picture of us in front of the Grand Canyon? W: Don't you think it's a little out of focus? Q: What does the woman imply? (...
A.
The photograph is not good enough to send.
B.
The photograph was not taken at the Grand Canyon.
C.
They already sent Mary a photograph of their vacation.
D.
Sending pictures through the mall is too expensive.
【单选题】设X, Y的方差存在,且不等于0,则D(X+Y)=DX+DY是X, Y
【单选题】设随机变量X和Y的方差存在且不等于0,则D(X+Y)=D(X)+D(Y)是X和Y( )
【简答题】根据汉语提示完成句子。 1. Timmy really doesn't understand why his parents so _____ (严格的). 2. The vote was completed. The teacher _____ (宣布) he result. 3. Can I see your car _____ (驾照)? 4. _____ (十六岁的青少年) shoul...
【简答题】补全对话 根据对话内容,在每个 标有题号的空白处填入一个适当的句子,使对话完整,合乎情景。 A: Hi , Tony . I didn't see you last Sunday . Did you go on a school trip ? B: 11. ______________________________. I stayed at home . A: Oh,really ? 12._...