Y, . Y:
X | -100 | Y | -1 | |||
p | 0,5 | 0,5 | p | 0,5 | 0,5 |
Y :
M[X] = -100×0,5+100×0,5 = -50+50 = 0
M[Y] = -1×0,5+1×0,5 = -0,5+0,5 = 0
Y . , , , .
, . . , , . , , M[X].
: [].
, 0:
[ []]=0.
, [ []]= [] M[[]]= [] M[]=0.
, , . 0. . , .
:
D[] = [( [])2]. (6.4)
, , , , , , , . (6.4) (6.3), :
D[] = =
× + × + + × . (6.5)
:
D[] = [2] ([])2. (6.6)
(6.6). , :
D[] = [( [])2] = [2 2××[]+ []2].
, [] , : D[] = [2]M[2××[]]+M[[]2] = [2] 2×([])2 +([])2 = [2] ([])2.
, D[] = [2] ([])2 = ([])2 = × + × + + × ([])2.
6.9. , :
X | |||
p | 0,2 | 0,5 | 0,3 |
6.6 : [X]=3,2. . D[X]=(1-3,2)2×0,2 + (3-3,2)2×0,5 + (5-3,2)2×0,3 = (-2,2)2×0,2 + (-0,2)2×0,5 + 1,82×0,3 = 4,84×0,2 + 0,04×0,5 + 3,24×0,3=1,96.
|
|
(6.6):
D[X]=12×0,2+32×0,5+52×0,33,22=1×0,2+9×0,5+25×0,310,24=0,2+4,5+7,510,24 =1,96.
, 2- (6.6) .
:
1. :
D[C]=0.
2. , :
D[C×]=C2×M[X].
3. :
D[+Y]=D[X]+D[Y].
4. :
D[ՖY]=D[X]+D[Y].
6.10. , ( 6.1):
X | ||
p |
, M[X]= . (6.5), :
D[X]=(0 )2× +(1 )2× = × + × = .
, p. : M[X]= p. :
D[X]=(0 p)2×(1 p)+(1 p)2× p = p ×(1 p) × (1 p + p)= p ×(1 p).
X n . . p, q =1 p.
D[X] n , p , :
M[X]= npq.
, 6.4 (n =3, p =0,6), D[X]= n×p × (1 p)= 3×0,6×0,4=0,72