Basic Probability: A ( B C ) ( A B) ( A C ) A ( B C ) ( A B) ( A C ) M X (0) 1 ( A B ) '
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Basic Probability: A ( B C ) ( A B) ( A C ) A ( B C ) ( A B) ( A C )
M X (0) 1
( A B ) ' A ' B ' ( A B ) ' A ' B '
M aX b (t ) etb M X (at ) P ( X 1 x1 , X 2 x2 ,..., X k xk )
M X (t ) E (etX ) etX p ( x ) MX
(n)
(0) x n p ( x) E ( X n )
n! x x x p1 1 p2 2 ... pk k x1 !x2 ! ... xk !
P ( A B ) P ( A) P ( B ) P ( A B ) P ( A B C ) P ( A) P ( B ) P (C ) P( A B) P ( A C ) P ( B C ) P ( A B C )
Continuous Random Variables n n! r !(n r )! r
b
P (a X b) f ( x)dx a
P( A B) P( B) P ( A B ) P( A / B ) P ( B ) P ( A '/ B) 1 P ( A / B) P ( A B / C ) P ( A / C ) P ( B / C ) P( A B / C ) P ( A) P ( A / B ) P ( B ) P( A / B ') P ( B ') P ( E ) P ( A1 E ) P ( A2 E ) ... P ( An E ) P( A / B)
f ( x)dx 1
F ( x) P ( X x) x
F ( x)
f (u )du
F '( x) f ( x ) P (a X b) F (b) F (a ) lim F ( x ) 1 x
Independence: P ( A / B ) P ( A) P ( A B ) P( A) P ( B ) Discrete Random Variables a (1 r n 1 ) 2 n a ar ar ... ar 1 r a a ar ar 2 ... ar n ... 1 r E ( X ) x p ( x) Mean E ( aX ) aE ( X ) E ( aX b) aE ( X ) b V ( X ) ( x ) 2 p ( x) E ( x ) 2 V (X ) 2 V (aX ) a 2V ( X ) V (aX b) a 2V ( X ) V ( X ) E ( X 2 ) E ( X )2
lim F ( x) 0
x
d d P (T t ) P(T t ) or F '( x) S '( x) dt dt E( X )
x f ( x)dx
E g ( X )
g ( x) f ( x)dx
M X (t ) E (e ) tX
e
x e
n ax
dx
0
cx xe dx
xecx ecx 2 c c
xn 0 x e ax
lim
n! a n 1
tx
f ( x)dx
E E ( X / Y ) E ( X )
Multivariate Distributions
E E (Y / X ) E (Y )
PX ( x ) p ( x, y )
V ( X / Y ) E ( X 2 / Y y) E ( X / Y y)
y
PY ( y ) p( x, y )
V ( X ) E V ( X / Y ) V E ( X / Y )
x
b d
V (Y ) E V (Y / X ) V E (Y / X )
a c
M X ,Y (t1 , t2 ) E (et1 X t2Y )
P (a X b, c Y d ) f ( x, y )dydx f X ( x)
M X ,Y (t1 , 0) E (et1 X ) M X (t1 )
f ( x, y )dy
fY ( y )
M X ,Y (t1 , t2 )t1 t2 0 t1
E (Y )
M X ,Y (t1 , t2 )t1 t2 0 t2
f ( x, y )dx
P( X x / Y y ) p( x / y ) f ( x / Y y) f ( x / y)
p ( x, y ) pY ( y )
f ( x, y ) fY ( y )
E ( X / Y y ) x p ( x / y ) E ( X / Y y)
M X ,Y (t1 , t2 )t1 t2 0 t1t2
p ( x / y ) p X ( x)
x f ( x / y )dx
p ( y / x) pY ( y )
f ( x / y ) f X ( x)
f ( x) P ( A)
f ( y / x ) fY ( y ) f ( x , y ) f X ( x ) f Y ( y )
E ( X Y ) E ( X ) E (Y ) Cov( X , Y ) E ( XY ) E ( X ) E (Y ) Cov( X , X ) V ( X ) Cov(Y , Y ) V (Y ) Cov( X , k ) 0 Cov(aX , bY ) abCov( X , Y ) Cov(W X , Y Z ) Cov(W , Y ) Cov(W , Z ) Cov( X , Y ) Cov( X , Z ) V ( X Y ) V ( X ) V (Y ) 2Cov( X , Y ) V (aX bY c ) a 2V ( X ) b 2V (Y ) 2abCov( X , Y ) V (aX bY cZ ) a 2V ( X ) b 2V (Y ) c 2V ( Z ) 2 abCov ( X , Y ) acCov ( X , Z ) bcCov(Y , Z ) Correlation Coefficient: XY
E ( XY )
Independence:
x
f ( x / A)
E( X )
Cov( X , Y ) V ( X ) V (Y )
E ( XY ) E ( X ) E (Y ) Cov( X , Y ) 0 V ( X Y ) V ( X ) V (Y ) M X Y (t ) M X (t ) M Y (t ) Sums of Distributions Single Bernoulli Binomial Poisson Geometric Negative Binomial Normal Exponential Gamma Chi-Square
Multiple Binomial Binomial Poisson Negative Binomial Negative Binomial Normal Gamma Gammas Chi-Square
2
If X,Y have joint distribution which is uniform, 1 then pdf is Area of R
E ( X ) ( x d ) f x ( x) dx (u d ) 1 Fx (u ) u
Area of A then P(A) = Area of R
u
1 Fx ( x) dx d
Bivariate Normal Cov( X , Y ) ( X E ( X )) V (X )
E (Y / X ) E (Y )
V (Y / X ) V (Y ) (1 2 XY ) Bernoulli = Binomial with only 1 trial Coefficient of Variation =
Memoryless Exponential, Uniform, Geometric Combine Normals Add/Subtract Means Add variances Deductibles and Policy Limits 0 xd
Deductible: Y
xd xd
d
d
E ( X ) ( x d ) f x ( x )dx 1 F ( x) dx x u
Policy Limit: Y
xu xu
u
u
0
u
0
E ( X ) xf x ( x)dx u f x ( x)dx xf x ( x)dx u 1 Fx (u ) dx u
1 Fx ( x ) dx 0
Deductibles and Policy Limits