You are part of a profiling unit for serious crimes The prob

You are part of a profiling unit for serious crimes. The probability that someone is a serial killer is 1 in a million. The probability that there is a murder in the neighborhood if there is a serial killer is 0.99. The lifetime probability of there being a murder in the neighborhood is one in a thousand but the probability of three murders in a neighborhood within a year is also 1 in a million. What is the probability that there is a serial killer on the loose if there were three murders within a year in the neighborhood? A. 0.5 B. 0.1 C. 1 D. 1 in a million E. 0.99

Solution

Probability that there is a serial killer on the loose if there were three murders within a year in the neighborhood = Probability that someone is a serial killer * probability of three murders in a neighborhood within a year / probability of three murders in a neighborhood within a year

= Probability that someone is a serial killer

= 1 in million

Hnece option D is correct