In this problem, you are asked to solve part of the Focus Problem at the
beginning of this chapter. In his book Chances: Risk and Odds in Everyday
Life, James Burke says that there is a \(72 \%\) chance a polygraph test (lie
detector test) will catch a person who is, in fact, lying. Furthermore, there
is approximately a \(7 \%\) chance that the polygraph will falsely accuse
someone of lying.
(a) Suppose a person answers \(90 \%\) of a long battery of questions
truthfully. What percentage of the answers will the polygraph wrongly indicate
are lies?
(b) Suppose a person answers \(10 \%\) of a long battery of questions with lies.
What percentage of the answers will the polygraph correctly indicate are lies?
(c) Repeat parts (a) and (b) if \(50 \%\) of the questions are answered
truthfully and \(50 \%\) are answered with lies.
(d) Repeat parts (a) and (b) if \(15 \%\) of the questions are answered
truthfully and the rest are answered with lies.