80 likes | 228 Views
Probabilistic Graphical Models. Independencies. Preliminaries. Independence. For events , , P if: P(, ) = P() P() P(|) = P() P(|) = P() For random variables X,Y, P X Y if: P(X, Y) = P(X) P(Y) P(X|Y) = P(X) P(Y|X) = P(Y). Independence. D. I.
E N D
Probabilistic Graphical Models Independencies Preliminaries
Independence • For events , , P if: • P(, ) = P() P() • P(|) = P() • P(|) = P() • For random variables X,Y, P X Y if: • P(X, Y) = P(X) P(Y) • P(X|Y) = P(X) • P(Y|X) = P(Y)
Independence D I P(I,D) G
Conditional Independence • For (sets of) random variables X,Y,Z P (X Y | Z) if: • P(X, Y|Z) = P(X|Z) P(Y|Z) • P(X|Y,Z) = P(X|Z) • P(Y|X,Z) = P(X|Z) • P(X,Y,Z) 1(X,Y) 2(Y,Z)
Conditional Independence Coin X1 X2
Conditional Independence I P(S,G | i0) G S
Conditioning can Lose Independences P(I,D | g1)