Applying Bayes’ Rule

E: The patient’s white blood cell count exceeds 110% of average.

H: The patient is infected with tetanus.

P(E|H) = 0.8 class-conditional probability

P(E|~H) = 0.3 “

P(H) = 0.01 prior probability

posterior probability:

P(E|H) P(H) (0.8) (0.01) 0.008

P(H|E) = ----------------- = -------------------------------- = ------- = 0.0262

P(E) (0.8) (0.01) + (0.3)(0.99) 0.305

P(E) = P(E|H) P(H) + P(E|~H)(1 - P(H))