(3rd-September-2020)
• This example also illustrates another example of explaining away and the preference for simpler diagnoses over complex ones.
• Before any observations, we can compute (see the next section), to a few significant digits, P(smokes)=0.2, P(influenza)= 0.05, and P(bronchitis)=0.18. Once wheezing is observed, all three become more likely: P(smokes|wheezing)=0.79, P(influenza|wheezing)= 0.25, and P(bronchitis|wheezing)=0.992.
• Suppose wheezing∧fever is observed: P(smokes|wheezing∧fever)=0.32, P(influenza|wheezing∧fever)=0.86, and P(bronchitis|wheezing∧fever)=0.998. Notice how, as in Example 5.30, when fever is observed, influenza is indicated, and so smokes is explained away.
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