已知随机变量X~N(5,9),Y=2X+3,下列说法正确的是
A: E(Y)=10,Var(Y)=18
B: E(Y)=13,Var(Y)=18
C: E(Y)=10,Var(Y)=36
D: E(Y)=13,Var(Y)=36
A: E(Y)=10,Var(Y)=18
B: E(Y)=13,Var(Y)=18
C: E(Y)=10,Var(Y)=36
D: E(Y)=13,Var(Y)=36
D
举一反三
- 若随机变量X与Y满足E(XY)=E(X)E(Y),则()。 A: Var(XY)=Var(X)Var(Y) B: Var(X+Y)=Var(X)+Var(Y) C: X与Y独立 D: 以上说法均不正确
- 设(X, Y)为二维随机变量,已知Var(X)=3, Var(Y)=6, Cov(X,Y)=2,则Cov(X+Y, Y) = A: 8 B: 9 C: 10 D: 6
- 如果随机变量X与Y满足: Var(X+Y)=Var(X−Y),则下列式子正确的是 A: X与Y相互独立 B: X与Y不相关 C: Var(X)=0 D: Var(X)Var(Y)=0
- 若随机变量X,Y满足Var(X+Y)=Var(X)+Var(Y),则X与Y相互独立.
- 设X,Y为两个随机变量,则下列各式中正确的是 A: E(X+Y)=E(X)+E(Y) B: Var(−CX)=−CVar(X) C: Var(X+Y)=Var(X)+Var(Y) D: [img=143x33]1803b3be61788d2.png[/img]
内容
- 0
Cans of soft drinks cost $0.30 in a certain vending machine. What is the expected value and variance of daily revenue (Y) from the machine, if X, the number of cans sold per day has E(X) = 90, and Var(X) = 40 ( ) A: E(Y ) = 27, Var(Y ) = 4.5 B: E(Y ) = 27 , Var(Y ) = 4.5 C: E(Y ) = 27 , Var(Y ) = 3.6 D: E(Y ) = 90 , Var(Y ) = 3.6
- 1
y 的输出结果是 var x=-10,y; x = 2*x; y = x+25;
- 2
若二维随机变量(X,Y)满足 Var(X﹣Y)=Var(X+Y),则X与Y不相关.( )
- 3
有下述JS代码:var x = 10; var y = 20;var z = x<y ? x++ : ++y ;console.log( ‘x=’ + x + ‘; y=’ + y + ‘; z=’ + z);其运行结果是( ) A: x=11; y=20; z=11 B: x=11; y=21; z=10 C: x=11; y=21; z=11 D: x=11; y=20; z=10
- 4
y 的输出结果是var x=-10 , y;x = 2*x;y = x+25; A: -15 B: 10 C: -5 D: 5