Applying Bayes’ Rule (cont.)
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Given:
P(S|M) = 0.5
P(M) = 1/50000
P(S) = 1/20
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What's the probability that a patient with a stiff
neck has meningitis?
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P(M|S) = P(S|M) P(M) / P(S)
= 0.5 * (1/50000) / (1/20)
= 0.5 * 20 / 50000 = 10/50000 = 1/5000