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A lie detector shows a positive signal (indicating a lie) 10% of the times a subject tells the truth and 94% of the time he lies. If two people are suspected of a crime that is known to have committed only one of them, and both claim to be innocent, what is the probability that a positive signal from the detector corresponds to the culprit?

I'm very confused solving this exercise. Can someone help me?

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Probability of a positive signal and a lie is the percentage when a positive signal is generated for a lie divided by the sum of the percentages for all positive signals (for both a lie and the truth). 94/(94+10) = .9038

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