A certain virus infects one in every 40 people. A test used to detect the virus in a person is positive 80% of the time if the person has the virus and 5% of the time if the person does not have the virus. (This 5% 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 and they have tested positive, i.e.find P(A and B). P(A and B) = b) Find the probability that a person has the virus given that they have tested positive, i.e. find P(A/B). P(A/B)= Question Help: Video Submit Question

A First Course in Probability (10th Edition)
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ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
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Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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A certain virus infects one in every 40 people. A test used to detect the virus in a person is positive 80% of
the time if the person has the virus and 5% of the time if the person does not have the virus. (This 5% 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 and they have tested positive, i.e.find P(A and B).
P(A and B) =
b) Find the probability that a person has the virus given that they have tested positive, i.e. find P(A/B).
P(A/B)=
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Transcribed Image Text:A certain virus infects one in every 40 people. A test used to detect the virus in a person is positive 80% of the time if the person has the virus and 5% of the time if the person does not have the virus. (This 5% 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 and they have tested positive, i.e.find P(A and B). P(A and B) = b) Find the probability that a person has the virus given that they have tested positive, i.e. find P(A/B). P(A/B)= Question Help: Video Submit Question
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E v e n t space A space colon space p e r s o n space i s space i n f e c t e d
E v e n t space B space colon space p e r s o n space t e s t s space p o s i t i v e
P left parenthesis A right parenthesis space equals space 1 over 40 space equals space 0.025
P left parenthesis A apostrophe right parenthesis space equals space 1 minus P left parenthesis A right parenthesis space equals space 1 minus 0.025 space equals space 0.975
P left parenthesis B vertical line A right parenthesis space equals space 0.80
P left parenthesis B vertical line A apostrophe right parenthesis space equals space 0.05

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