1.pC3、6+CC7C2x8=067 2.PX<50}=P 50-40 =d(l)=0.8413 令Y= 则Y~B(5,0.8413),因此 P{=2}=C30.8413(1-0.8413)3=00283 10≤x≤1 10≤y≤1 3.f(x) 0其它 0其它 所以(xy)=()(0)=10x105y31 Px+y 4.E(X)=0.9,D(x)=061 P{x-4-=1-02=098,故 2Φ -1=0.98,d =0.99 =2.325,σ=544 6.X~N(66.5,),设H:X=70,H1:X≠70,则 X--1(n-1),故拒绝域为1. 0.67 10 8 10 7 10 6 2 12 2 4 2 12 1 4 1 8 2 12 2 8 = + + = C C C C C C C P 2. (1) 0.8413 10 50 40 { 50} = = − P X = P , 令 10 − 40 = x Y ,则 Y ~ B(5,0.8413) .因此 { 2} 0.8413 (1 0.8413) 0.0283 2 2 3 P Y = = C5 − = . 3. = 0 其它 1 0 1 ( ) x f x , = 0 其它 1 0 1 ( ) y f y 所以 = = 0 其它 1 0 1,0 1 ( , ) ( ) ( ) x y f x y f x f y 故 25 17 5 6 = P X + Y〈 . 4. E(X ) = 0.9, D(X ) = 0.61. 5. ~ ( , ) 2 n X N ,而 P| X − | 4= 1− 0.02 = 0.98 ,故 1 0.98 4 2 − = n , 0.99 4 = n , 2.325 4 = n , = 5.44. 6. ~ (66.5, ) 2 n X N ,设 H0 : X = 70 , H1 : X 70 ,则 ~ ( −1) − = t n n S X t ,故拒绝域为