2010
51
22.14
54
( 2 24 2010 )
: .., .., ..
: ..
: . ..
. . . .
.
- . , , , .
X F(x), x , X , x, ..
F(x) = (X < ).
:
1) [0;l]:
≤ F(x) 1.
2) :
F( )≥ F( ), > .
3) , X [ a;b), a b:
F(a ≤ X<b)=F(b)-F(a).
4 ) ( ≥ x) =1 - F(x).
5) → + ∞, F(x) → 1.
6) → - ∞, F(x)→ 0.
, , .
x1., x2, x3, X p1, p2, p3, (pi=P(X=xi)), p1+p2+p3+=1. , . X, - :
X | x1 | x2 | x3 | |
p | p1 | p2 | p3 |
, (xi,pi) . X.
2.1 . 7 , 4 , . 3 ; - . .
|
|
. : 0, 1, 2, 3. p0, p1, p2, p3 :
;
;
X
X | ||||
p | 1/35 | 12/35 | 18/35 | 4/35 |
: 1/35+12/35+18/35+4/35=1. 1.
F(x).
x 0, F(x)=P(X<x)=0
0<x 1, F(x)= p0=1/35
1<x 2, F(x)= p0+ p1=1/35+12/35=13/35
2<x 3, F(x)= p0+ p1+ p2=31/35
x>3, F(x)= p0+ p1+ p2+ p3=1
,
F(x)=
2
, .
M [ X ] X xi
M[X]= xi pi (1)
:
1) , M [ c ] =c;
2) M[c X]=c M[X];
3) X Y , M[X Y]=M[X] M[Y];
4) M[X+Y]=M[X]+M[Y].
()
D[X]=M[(X-M[X]) ]. (2)
D[X] =M[X ]-M[X] . (2)
:
1) c , D [c]=0;
2) D [c X ]=c D[X];
3) X Y , D [ X+Y ]= D [ X ]+ D [ Y ]
.
X
σ[ X ]= (3)
2.2 . 1 . 0,7, 0,8, 0,9. Z .
. X i i (i =1,2,3),
Xi
Z=X1+X2+X3, M[Z]=M[X1+X2+X3]=M[X1]+M[X2]+M[X3]
X1 | ||
p | 0,3 | 0,7 |
X2 | ||
p | 0,2 | 0,8 |
X3 | ||
p | 0,1 | 0,9 |
M[X1]=0,7; M[X2]=0,8; M[X3]=0,9
M[Z]= M[X1+ X2+ X3]=0,7+0,8+0,9=2,4.
:
2.3 , ,
X | -2 | |||
p | 0,1 | 0,4 | 0,3 | 0,2 |
(3,1; 13,89)
2.4 X 4 : =1, =3, =4, =6. = 0,1, = 0,4, =0,2. X.
2.5 X : = 2 = 0,3, = 4 = 0,4 . , , M[X] =5. (9,33; 0,3).
2.6 . , 2 , 15. (≈ 1,042)
|
|
2.7 [X] D [ X ] X , , 100 , 0.05. (5; 4,75)
2.8 X - 20 , 0.3. (4.2)
2.9 X , | > | |. , X 0,3. X, , [] = 3,4; D [ X ]= 0,84.
2.10 5 3 . 2 , X - .
2.11 , ? (21/2).
2.12 X - 5 . : ) ; ) ; ) ; - 2, 3 ; - 3 ; - . (5/8; 13/16; 13/16).
2.13 0,7 , 4 , X - , ) X. ) . ) : X < 2; X ≤ 3; 1 < X ≤ 3. (0,91; 0,9919; 0,0819)
2.14 7 , 4 - . 3 . ) X, . ) . ) : 0 < X ≤ 2. (6/7)
2.15 25 , 5 "", 3 . , X, "" . X > 0?(0,6; 0,44; 58/115)
2.16 5 , . , X, , . (3;2)
2.17 10 8 . 2 . , X, . (1,6; 0,2855)
2.18 . X . X X ≤ 5. (0,335)
2.19 6 , , 0,5. , X, , . (0,656; 1,788)
2.20 0,1. , , , . , .., 5 . , X, . (4,095; 1,9889)
|
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2.21 5 . , . , 0.9,
2;22 X: 1 = 1, x2 = 2, 3 = 3, [] = 2,3, M[X2] = 5.9. X.