tats
posted by Help please! on .
No(Did not lie) Yes(lied)
positive test result 15(false positive) 42(true positive)
negative test result 32(true negative) 9 (false negative)
Refer to table and assume that one of the 98 test subjects is randomly selected. Find the probability of selecting a subject with a negative test result, given that the subject lied. WHat does this result suggest about the polygraph test?

Given that all the answers are mutually exclusive (total=15+42+32+9=98), i.e. no answer can be counted more than once, and the subject lied with a negative result means that he/she is in the false negative category(9).
So the probability is 9/98.