"xy相互独立则D(xy)=D(x)D(y)"...xy相互独立则D(xy)=D(x)D(y)

　"xy相互独立则D(x+y)=D(x)+D(y)"...xy相互独立则D(x+y)=D(x)+D(y)

　"xy相互独立则D(x-y)="...xy相互独立则D(x-y)=

　"xy相互独立则D(x-y)=D(x)+D(y)"...xy相互独立则D(x-y)=D(x)+D(y)

　"xy相互独立则DXY"...xy相互独立则DXY

　"xy相互独立则DX与DY"...xy相互独立则DX与DY

　"xy相互独立则D(xy)"...xy相互独立则D(xy)

　"xy相互独立则E(xy)=E(x)E(y)"...xy相互独立则E(xy)=E(x)E(y)

　"xy相互独立则x^2与y^2"...xy相互独立则x^2与y^2

　"xy相互独立则cov(x,y)=0"...xy相互独立则cov(x,y)=0