X
X x
1
x
n
p
1
p
n
x
1
, ..., x
n
p
1
, ..., p
n
F (x) = P (X < t) =
X
j:x
j
<t
p
j
.
MX =
n
X
k=1
x
k
p
k
.
DX = M(X −MX)
2
.
M(X + Y ) = MX + MY, M(αX) = αMX, D(αX) = α
2
DX,
X, Y
MXY = MX MY, D(X + Y ) = DX + DY.
σ =
√
DX X
(MX − 3σ, MX + 3σ)
X
ρ(X, Y ) =
cov(X, Y )
√
DXDY
,
cov(X, Y ) = MXY − MXMY = M(X −MX)(Y − MY )
X Y
ρ
X Y ρ(X, Y ) = 0
ρ
| ρ(X, Y ) | < 1/3
X Y 1/3 ≤| ρ(X, Y ) | < 2/3 | ρ(X, Y ) | ≥ 2/3
ρ > 0