: ,
F(x) , x, .. F(x) = { £ }. , , 1 2, , :
P{x1 < X £ x2}= F(x2) F(x1). (1.2)
P{X > x} = 1 F(x). (1.3)
:
1) lim F(x) = F (- ¥) = 0;
2) lim F(x) = F (¥) = 1;
3) F(x) ³ 0;
4) F(x2) ³ F(x1), x2 > x1.
, .
F(x) . 1.1.
F(x) , :
(D x > 0). (1.4)
, , . ( ).
:
1) f(x)³ 0;
2)
3)
4) (z ).
. ,
= (1.5)
, , , , 1, 1 (. 1.2, ); , , 2, 2 (. 1.2, ); , , 1 2, 1 2 (. 1.2, ).
, . . , ( ) .
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. 1.2
) ) )
mx ( ):
(1.6)
mx :
=
mx, . mx , . s x.
( ) . X, Y () : F(x, y) f(x, y). F(x, y), , , x, y, :
F(x,y) = P{X £ x; Y£ y}. (1.8)
, F(x,y) , , ( ):
f(x, y)= (1.9)
f(x, y) :
1) f(x, y) ³ 0;
2)
3)
4) (z1 z2 ).
, X, Y W,
P{(X,Y)Î W} = (1.10)
,
P{a1 < X £ a2; b1 < Y £ b2} = . (1.11)
f(x, y) () f(x), f(y) :
f(x) = f(y) =
X Y ,
f(x) f(y). (1.13)
, X Y . , , , mx, my, , X Y. ( ).
cov(X, Y) = ) f(x,y) dx dy, (1.14)
rxy = . (1.15)
, X Y. -1 £ rxy £ 1. rxy = 1, , .. y = a0 + a1 x, a0, a1 , a1 > 0. rxy = -1, , .. y = a0 - a1. rxy = 0, , X Y : a1 = 0. , X Y , rxy = 0; , . : X Y ( , , ).
, . () .