第 概率统
第六章习题课 《概率统计》
6+1 E(x)=∑E(X) 6+2 D(X)=E(X)-(EX)96+10+1 6+30+2 正确求解 D()=G=D)1 EX2-(EX n n 0+1(+1) 6+1 n+3(+2)2」m(0+3+2)
6 -1(3) 21 ( ) 1 ( ) 1 ++ = = = n i E Xi n E X 2 2 2 ) 21 ( 31 ( ) ( ) ( ) ++ − ++ = − = D X E X E X ? 正确求解 2 2 2 ( ) ( ) 1 ( ) i i i EX EX n n D X n D X = = = − 2 2 2 ( 3)( 2) 1 ( 2) ( 1) 3 1 1 + + + = ++ − ++ = n n
仿P:191~-192求得E(S2)<2 a2与题无关,等于没求! 正确求解 6+1 E(S2)=0=D(X) (0+3)(+2)2 6-2(1) 9 CNP(1-p) k=0.1….N x怎能取两项概率?
2 2 2 ( 3)( 2) 1 ( ) ( ) + + + = = = D Xi E S 仿P.191~192 求得 2 2 E(S ) = 2 与题无关，等于没求！ 正确求解 6-2 (1) ( ) = = − = − k N x C p p x x k k N k i N n 0,1, , (1 ) , , , 1 ? xi 怎能取两项概率?
正确求解 x.=0.1.….N (1)Q i=1,2,…,nk是 再看 什么? ()F(x,…x)=cp1-P) (3)E(X)=∑B(X)=∑和=m E(S2)=和(1-p) 注意二项分布的参数是什么?
(3) np np n E X n E X n i n i = i = = =1 =1 1 ( ) 1 ( ) ( ) (1 ) 2 E S = np − p 正确求解 ( ) = = = i n x N x x i n 1,2, , 0,1, , , , 1 (1) 2 1 0 1 1 1 0 ( , , ) (1 ) = − = − i x k N k N F x x C p p i (2) 再看 k 是 什么？ 注意二项分布的参数是什么？
正确求解 (2)P(H1=x12…X1o=x0) ∏cwp3(1-p)x 10N-∑x10 p(1-p)∏ 个4 0,1,…,N,i=1,2,…,10 (3)E(X)=Np E(S2)=Np(1-p)
(2) = − = − − = = − = = = = 1 0 1 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 (1 ) (1 ) ( , , ) i x N x N x i x x N x N i i i i i i i i p p C C p p P X x X x x = 0,1, ,N, i =1,2, ,10. i (3) E(X ) = N p ( ) (1 ) 2 E S = N p − p 正确求解