4.2 Medical Testing
Score: 4.38/7 Answered: 5/7
• Question 5
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A certain virus infects one in every 300 people. A test used to detect the virus in a person is positive 80% of
the time if the person has the virus and 8% of the time if the person does not have the virus. (This 8% result is
called a false positive.) Let A be the event \"the person is infected\" and B be the event \"the person tests
positive\" .
a) Find the probability that a person has the virus given that they have tested positive, i.e. find $P(A|B)$. Round
your answer to a percent rounded nearest fourth decimal place and do not include a percent sign.
P(A|B)=
%
b) Find the probability that a person does not have the virus given that they test negative, i.e. find $P(A'|B')$.
Round your answer as a percent rounded to the nearest fourth decimal place and do not include a percent
sign.
P(A'B') =
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