Question 189177:  Radio station WQXP has 15% of the market in Houston and 40% of the market in Dallas.  Of the total number of radio listeners in Houston and Dallas, 85% live in Houston and 15% in Dallas. 
If you know that the listener is indeed listening to station WQXP, what then is the probability that the listener lives in Dallas? 
 Answer by stanbon(75887)      (Show Source): 
You can  put this solution on YOUR website! Radio station WQXP has 15% of the market in Houston and 40% of the market in Dallas. Of the total number of radio listeners in Houston and Dallas, 85% live in Houston and 15% in Dallas. 
If you know that the listener is indeed listening to station WQXP, what then is the probability that the listener lives in Dallas? 
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P(Dallas|WQ) = [P(D and W)] / [P(w and D) + P(W and H)] 
= [P(w|D)*P(D)]/{[P(w|D)*P(D)] + [P(W|H)*P(H)]} 
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You have P(H) = 0.85 ; P(D) = 0.15 ; P(W|H) = 0.15 ; P(W|D) = 0.40 
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Make your substitutions to get the answer. 
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This is Bayes way of doing it. 
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Cheers, 
Stan H. 
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