般治影办建应者时干经战家率常受确约们却之设X与Y相互独立,D(X)=3,D(Y)=2,则协方差cov(2XY,X-2Y)=___般治影办建应者时干经战家率常受确
1Var [X + Y ] = Var [X] + 2Cov (X,Y ) + Var [Y]就用定义证明就行,Var(X)=E(X^2)-[E(X)]^2Var(Y)=E(Y^2)-[E(Y)]^2Cov(X,Y)=E(XY)-E(X)E(Y)所以Var [X + Y ]=E[(X+Y)^2]-[E(X+Y)]^2=E(X^2+2XY+Y^2)-[E(X)+E(Y)}^2={...结果...
E(X)=5*0.1=0.5,D(X)=5*0.1*0.9=0.45 E(Y)=1,D(Y)=4;E(X-2Y)=E(X)-2E(Y)=0.5-2=-1.5 D(X-2Y)=D(X)+4D(Y)=0.45+4*4=16.45 E((X+Y)²)=E(X²+Y²+2XY)=E(X²)+E(Y²)+E(2XY)=D(X)+E(X)²+D(Y)+E...
Cells were sorted into 5mL FACS tubes containing 1mL of 2xYPAD supplemented with 1% BSA. Tubes were pre-wet with collection media prior to sample collection, to reduce sticking and improve post-sort yield. For expression sorts, cells were gated for singleton events (Figure S2A), followed by...
【题目】设X,Y为随机变量,E(X)=E(Y)=1,Cov(X,Y)=2,则E(2XY)= A.-6 B.-2 C.2 D.6查看答案 纠错 收藏 相关推荐在持有期为2天、置信水平为98%的情况下,若所计算的风险价值为2万元,则表明该银行的资产组合()。 下列关于会计信息质量的要求,说法正确的有()。 甲公司为小型微利企业,2019年度...
解析 答: 证明: D(X+Y)=E[(X+Y)2]-E2(X+Y) =E(X2+2XY+Y2)-[E(X)+E(Y)]2 =E(X2)+2E(XY)+E(Y2)-E(X2)-2E(X)E(Y)-E2(Y) =[E(X2)-E2(X)]+[E(Y2)-E2(Y)]+2[E(XY)-E(X)E(Y)] =D(X)+D(Y)+2Cov(X,Y) 同理D(X-Y)=D(X)+D(Y)-2Cov(X,Y)...
2f). A magnesium ion in nsp16 of the previous CoV outbreak strain (PDB ID: 2XYR) binds to a remote site constituted by T58 and S188 located at the opposite face of the catalytic pocket (Supplementary Fig. 2)13. A direct binding of metals in the substrate/catalytic pocket and their ...
If f(x,y)= 1/2xy^2+1/2yx^2, and 0 is less than x is less than 1 and 0 is less than y is less than 2: a. Show that f(x,y) is a joint pdf. b. Find Pr( x is greater than y), Pr(y is greater than x)...
维随机变量(X,Y)的联合概率密度函数为10x1,0y2f(x,y)=0,其它求Cov(X,Y) 相关知识点: 试题来源: 解析 解: f_xx=∫_0^xf(x,y)dy=∫_0^22dy=1 f(x_1)=∫_0^1f(x,y)dx=∫_0^11/2dx=1/2 E(x_4)=∫_0^1dx∫_0^2xydy=∫_0^1(1/2xy^2)l_0^2dx=∫_0^12 ...
其中,E(X)E(X)E(X) 是随机变量 XXX 的期望。 现在,我们考虑两个随机变量 XXX 和YYY 的和X+YX+YX+Y 的方差: 根据方差的定义,我们有: D(X+Y)=E[(X+Y−E(X+Y))2]D(X+Y) = E[(X+Y - E(X+Y))^2]D(X+Y)=E[(X+Y−E(X+Y))2] 展开平方项,得到: D(X+Y)=E[X2+2XY+...