概率和数理统计

2.0.2

3.0.3413

4.1

5.四

6.0

7.8.题目不完整

9.题目不清楚

10边缘分布x = 0p = 1/4+1/6+1/8 = 13/24x = 1p = 1-13/。

Y = 0 P = 1/4+1/4 = 1/2Y = 1 P = 1/6+1/8 = 7/24Y = 2 P = 1/8+1/12 = 5/24

EX = 11/24 EY = 7/24+2 * 5/24 = 17/24

11k = 1/8 ex^2=8 p(-2 & lt；X & lt2)=1/4

12 X = 0 P = 0.01 X = 1 P = 0.18 X = 2 P = 0.81

Y =-1p = 0.01y = 1p = 0.18y = 3p = 0.81

25合格(20.01-20)/(0.203 * 3)= 0.148