概率论,

3
1）f(x,y)=1/(2*1)=1/2
2) fx(x)=∫(0~1) 1/2 dy
=1/2
fy(y)=∫(0~2) 1/2 dx
=1
3）=1-P(Y>=X²)
=1-∫(0~1)∫(x²~1) 1/2 dydx
=1-∫(0~1)(1-x²)/2 dx
=1- {(x-x³/3)/2|0~1}
=2/3
4
E(X)= ∫(0~1) (a+1)x^(a+1) dx
=(a+1)/(a+2)
Xbar(a+2)=a+1
(Xbar-1)a=1-2Xbar
a=(1-2Xbar)/(Xbar-1)
5
E(^u1)=(2+3+2)u/7=u
E(^u2)=(4+3+5)u/12=u
D(^u1)=(4+9+4)2²/49=17*4/49=4(2448/(49*144))
D(^u2)=(16+9+25)*4/144=50*4/144=4(2450/(49*144))
u1稍比u2有效
6.
={86.6-2.13(12)/4,86.6+2.13*(12)/4}
={80.21 ,92.99}