设随机变量(X,Y)的联合概率密度为f(x,y)=8xy,0<x<1,0<y<x;0,其他,答:-∞->+∞) f(x,y)dy=∫(0->x) 8xydy=4x^3,fY(y)=∫(-∞->+∞) f(x,y)dx=∫(y->1) 8xydx=4(y-y^3),所以 fX(x)=4x^3, 0<x<1,0,其他 fY(y)=4(y-y^3), 0<y<1 0 , 其他 (2)P{Y<=x/2}=∫(0->1)dx ∫(0->x/2) 8xydy=1/4 ...
设随机变量X,Y的联合概率密度为f(x,y)=k,0<x<1,0<y<x,求k答:2012-06-30 设随机变量(X,Y)的概率密度为f(x,y)=x+y,0<x... 173 2016-07-01 设随机变量x~b(4,1/2),则e(x^2+1)= 23 2012-12-05 设随机变量(X,Y)的联合概率密度为f(x,y)={kx,0... 6 2018-01-09 设随机变量X-N(0 1)求Y=e^x概率密度? 1 2012-07-03 设(X,Y)的概...
设二维连续型随机变量(X,Y)的联合概率密度为f(x,y)=(1+xy)/4,│x│...答:x,y是均匀分布 (2) E(X)=0,E(y)=0 D(X)=∫f(x)x²dx=1/3 ,D(Y)=∫f(y)y²dy=1/3 (3)f(x,y)≠f(x)f(y)故X和Y不独立。E(XY)=∫∫f(x,y)xydxdy=1/9 cov(x,y)=E(XY)-E(X)E(Y)=1/9 ρ=cov(x,y)/(√D(X)√D(Y))=1/3 x,y相关...