Formulario del corso di Statistica I Ingegneria Gestionale
a.a. 2009/10 x = x
1+:::+x n
n, S 2 = n 1 1 P n
i=1 (x i x) 2 , d Cov = n 1 1 P n
i=1 (x i x) (y i y), r = S Cov d
x{X
S
Y=
P
ni=1
(x
ix)(y
iy)
p P
ni=1
(x
ix)
2P
ni=1
(y
iy)
2. P n
i=1 (x i x) 2 = P n i=1 x 2 i nx 2 , P n
i=1 (x i x) (y i y) = ( P n
i=1 x i y i ) nxy.
n! = n (n 1) 2 1, 0! = 1. n k = k!(n k)! n! = n (n 1) k! (n k+1) . P (AjB) = P (A P (B) \B) , P (A \ B) = P (AjB) P (B). A; B indipendenti:
P (A \ B) = P (A) P (B), P (AjB) = P (A), P (BjA) = P (B). P (A) = P
k P (AjB k ) P (B k ). P (BjA) = P (A P (A) jB)P (B) .
X discreta, valori a j , P (X = a j ) = p j , allora E [X] = P
j a j p j , E [g (X)] = P
j g (a j ) p j , E X 2 = P
j a 2 j p j . P (X 2 A) = P
i:a
i2A P (X = a i ) = P
i:a
i2A p i . X 2 N, P (X n) = P n
i=0 p i , P (X n) = P 1
i=n p i . X continua, densità f (x), allora E [X] = R 1
1 xf (x) dx, E [g (X)] = R 1
1 g (x) f (x) dx, in particolare E X 2 = R 1
1 x 2 f (x) dx. P (X 2 A) = R
A f (x) dx.
V ar [X] = 2 X := E h
(X X ) 2 i
dove X = E [X]. V ar [X] = E X 2
2
X . Cov (X; Y ) = E [(X X ) (Y Y )], Cov (X; Y ) = E [XY ] X Y . (X; Y ) = Cov(X;Y )
X Y
. 1 (X; Y ) 1.
E [aX + bY + c] = aE [X]+bE [Y ]+c. V ar [X + Y ] = V ar [X]+V ar [Y ]+
2Cov (X; Y ). V ar [aX] = a 2 V ar [X]. Standardizzazione di X: X
XX
. X; Y indipendenti: P (X 2 A; Y 2 B) = P (X 2 A) P (Y 2 B). Implica E [XY ] = E [X] E [Y ], Cov (X; Y ) = 0, (X; Y ) = 0, V ar [X + Y ] = V ar [X] + V ar [Y ].
F (x) = P (X x). F (t) = R t
1 f (x) dx. F 0 (t) = f (t). F (q ) = . ' (t) = E e tX , ' 0 (0) = E [X], ' 00 (0) = E X 2 ; ' aX (t) = E e taX = ' X (at). X; Y indipendenti implica ' X+Y (t) = ' X (t) ' Y (t).
X B (n; p): P (X = k) = n k p k (1 p) n k , E [X] = np, V ar [X] = np (1 p), = p
np (1 p), ' (t) = (q + pe t ) n dove q = 1 p. X 1 ; :::; X n
B (1; p) indipendenti implica S = X 1 + ::: + X n B (n; p).
X P ( ): P (X = k) = e k!
k, E [X] = , V ar [X] = , = p , ' (t) = e ( e
t1 ). Se np n = allora lim n !1 n
k p k n (1 p n ) n k = e k!
k.
1
X N ; 2 : f (x) = p 1
2
2exp (x 2
2)
2. E [X] = , V ar [X] =
2 , ' (t) = e t e
t222. X; Y gaussiane indipendenti, a; b; c 2 R implica aX + bY + c gaussiana. X N ; 2 si può scrivere come X = Z + , con Z N (0; 1). F ;
2(x) = x . ( x) = 1 (x). q = q 1 . Soglie q .
X Exp ( ): f (x) = e x per x 0, zero per x < 0. E [X] = 1 , V ar [X] = 1
2, = 1 , ' (t) = t per t < . F (x) = 1 e x per x 0, zero per x < 0.
TLC: P X
1+:::+X p n
nn 2 A P (Z 2 A), con Z N (0; 1).
X = X
1+:::+X n
nN ; n
2. E S 2 = 2 . S
22(n 1) 2 n 1 .
= X q p
1 2n ; = X S t
(n 1) 1 2
p n .
x
0p
n > q 1
2. x S
0p
n > t (n 1) 1
2
. P jZj > x S
0p n , P X 2 h
0
q p
1 2n ; 0 + q p
1 2n
i .
S
22
(n 1) > 2 ;n 1 . T = n P k
i=1 (b p
ip
i)
2p
i= P k
i=1
( X b
inp
i)
2np
i> 2 ;k 1 . y = A + Bx, B = Cov d S
2X
= r S S
YX