SOLUTION: One-hour carbon monoxide concentrations in air samples from a large city have an approximately exponential distribution with mean 3.6 ppm (parts per million). a, find the probabil

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Question 331510: One-hour carbon monoxide concentrations in air samples from a large city have an approximately exponential distribution with mean 3.6 ppm (parts per million).
a, find the probability that the carbon monoxide concentration exceeds 9 ppm during a randomly selected one-hour period.
b, a traffic-control strategy reduced the mean to 2.5 ppm. Now find the probability that the concentration exceeds 9 ppm.
Answer by jrfrunner(365) About Me  (Show Source):
You can put this solution on YOUR website!
if x is exponentially distributed then
fx+=+%281%2Fmu%29+%2Ae%5E%28-x%2Fmu%29
+P%29x%3Ea%29+=+e%5E%28-a%2Fmu%29
in part 1, mu=3.6 and a=9
so P%28x%3E9%29+=+e%5E%28-9%2F3.6%29+=0.082 or 8.25%
in part 2, mu=2.5 and a =9
so P%28x%3E9%29+=e%5E%28-9%2F2.5%29+=0.0273 or 2.7%