设随机变量X,Y,Z相互独立,且X~N(4,5),Y~N(-2,9),Z~N(2,2),则P{0≤X+Y-Z≤3}=_______.(Φ(3/4)=0.7734)

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问题 设随机变量X,Y,Z相互独立,且X~N(4,5),Y~N(-2,9),Z~N(2,2),则P{0≤X+Y-Z≤3}=_______.(Φ(3/4)=0.7734)

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答案E(X+Y-Z)=EX+EY-EZ=4-2-2=0,D(X+Y-Z)=DX+DY+DZ=5+9+2=16,∴X+Y-Z~N(0,16),故P(0≤X+Y-Z≤3}=[*]=0.7734-0.5=0.2734.

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