For next 4 questions, use the following information: A missile protection system
ID: 3217951 • Letter: F
Question
For next 4 questions, use the following information: A missile protection system consists of n radar sets operating independently, each with a probability .9 of detecting a missile entering a zone that is covered by all of the units.
Let X be the number of radar sets which detect an incoming missile. How is X distributed? Be sure to explain your answer.
If n=5 and a missile enters the zone, what is the probability that exactly 4 sets detect it?
If n=5 and a missile enters the zone, what is the probability that at least 1 set detects it?
What is the expected proportion of missile sets that will detect an incoming missile when n=20?
Explanation / Answer
X is a binomial distribution as the events are either detecting or not detecting and the probability of events doesnt change
probability that exactly 4 sets detect it = 5C4 x 0.94 x0.1 = 0.328
probability that at least 1 set detects it = 1 - probability of none detecting
= 1 - 0.15 = 0.99999
when n = 20, expected proportion of missile sets that will detect an incoming missile = np = 0.9x20 = 18
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