Future Electronics makes compact disc players. Its research department found tha
ID: 3181286 • Letter: F
Question
Future Electronics makes compact disc players. Its research department found that the life of the laser beam device is normally distributed, with mean 5260 hours and standard deviation 440 hours. (a) Find the probability that the laser beam device will wear out in 5000 hours or less. (Round your answer to four decimal places.) (b) Future Electronics wants to place a guarantee on the players so that no more than 12% fail during the guarantee period. Because the laser pickup is the part most likely to wear out first, the guarantee period will be based on the life of the laser beam device. How many playing hours should the guarantee cover? (Round your answer down to the nearest hour.) Express Courier Service has found that the delivery time for packages is normally distributed, with mean 13 hours and standard deviation 3 hours. (a) For a package selected at random, what is the probability that it will be delivered in 18 hours or less? (Round your answer to four decimal places.) (b) What should be the guaranteed delivery time on all packages in order to be 95% sure that the package will be delivered before this time? ()Explanation / Answer
a)P(X<5000) =P(Z<(5000-5260)/440)=P(Z<-0.5909)=0.2773
b)for 12%, z=-1.175
hence corresponding value =mean +z*std deviation=4743 Hour
11)a)P(X<18)=P(Z<1.6667)
=0.9522
b)for 5% ; z=-1.6449
hence corresponding value =mean +z*std deviation= 8.1
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