Back to 5.3 Problems on Conditional Independence

5.3 Exercise 7

Avg difficulty 2.5

A real estate agent in a neighborhood heavily populated by affluent professional persons is working with a customer. The agent is trying to assess the likelihood the customer will actually buy. His experience indicates the following: if H is the event the customer buys, S is the event the customer is a professional with good income, and E is the event the customer drives a prestigious car, then

P ( S ) = 0 . 7 P ( S | H ) = 0 . 90 P ( S | H c ) = 0 . 2 P ( E | S ) = 0 . 95 P ( E | S c ) = 0 . 25 P \left(S\right) = 0 . 7 P \left(\right. S \left|\right. H \left.\right) = 0 . 90 P \left(\right. S \left|\right. H^{c} \left.\right) = 0 . 2 P \left(\right. E \left|\right. S \left.\right) = 0 . 95 P \left(\right. E \left|\right. S^{c} \left.\right) = 0 . 25

Since buying a house and owning a prestigious car are not related for a given owner, it seems reasonable to suppose P(E|HS)=P(E|HcS)P \left(\right. E \left|\right. H S \left.\right) = P \left(\right. E \left|\right. H^{c} S \left.\right) and P(E|HSc)=P(E|HcSc)P \left(\right. E \left|\right. H S^{c} \left.\right) = P \left(\right. E \left|\right. H^{c} S^{c} \left.\right). The customer drives a Cadillac. What are the odds he will buy a house?

Pfeiffer, Applied Probability, 5.3 Problems on Conditional Independence, exercise 7

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Adapted from Applied Probability © 2009 Paul E. Pfeiffer. Licensed under CC BY 3.0. Source: Applied Probability. Imported at revision d7a0420.