<PRE><B>Question 855067</B>
Suppose, if someone has been using the drugs, two different tests have probabilities of 99% and 95% respectively, of coming back positive. Assume independence of events. 
A) What is the probability, if someone has been using the drugs, that both tests come back negative? (Express your answer as a percent, without rounding.)
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Ans: 0.01*0.05 = 0.0005
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B) What is the probability, if someone has been using the drugs, that at most one of the tests come back negative? (Express your answer as a percent.)
P(at most one) = 1 - P(2 come back negative) = 1 - 0.0005 = 0.9995
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Cheers,
Stan H.

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