Given the following Bayesian Network consisting of four Bernoulli random variables and the associated conditional probability tables: P(V=0) = 0.5, P(V=1) = 0.5 P(U=0|V=0) = 0.5, P(U=1|V=0) = 0.5 P(U=0|V=1) = 0.5, P(U=1|V=1) = 0.5 P(W=0|U=0) = 1, P(W=1|U=0) = 0 P(W=0|U=1) = 0, P(W=1|U=1) = 1 P(Z=0|V=0,W=0) = 0.5, P(Z=1|V=0,W=0) = 0.5 P(Z=0|V=0,W=1) = 1, P(Z=1|V=0,W=1) = 0 P(Z=0|V=1,W=0) = 0.5, P(Z=1|V=1,W=0) = 0.5 P(Z=0|V=1,W=1) = 0.5, P(Z=1|V=1,W=1) = 0.5 The value of P(U=1, V=1, W=1, Z=1) is ______ (rounded to three decimal places).
GATE 2024 · Engineering Mathematics · Bayesian Network · medium
Answer: P(U=1, V=1, W=1, Z=1) = 0.125
- Write the joint probability using the Bayesian network factorization: The network structure gives: V is root, U depends on V, W depends on U, Z depends on V and W.
- Look up each CPT entry: From the given tables: P(V=1)=0.5; P(U=1|V=1)=0.5; P(W=1|U=1)=1 (deterministic); P(Z=1|V=1,W=1)=0.5.
- Multiply all factors: P = 0.5 * 0.5 * 1 * 0.5 = 0.125