Suppose your friend just took a home pregnancy test and the result was positive That particular brand advertises a positive result 91 of the time when given to a pregnant woman and a negative result 99 of the time when given to a woman who is not pregnant Before the test was taken your friend thought her chance of being pregnant was 50 50 Now given the positive result what is her new chance of being pregnant 0 989 0 819 0 099 0 5 O 0 91