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Author Question: The length of life of a certain type of washer is approximately normally distributed with a mean of ... (Read 94 times)

cdr_15

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on: Jul 24, 2018
The length of life of a certain type of washer is approximately normally distributed with a mean of 6.2 years and a standard deviation of 1.4 years. What period of time should the manufacturer give as a guarantee if it is willing to replace only 0.5 of the machines?

Question 2

The length of life of a certain type of washer is approximately normally distributed with a mean of 6.2 years and a standard deviation of 1.4 years. If this machine is guaranteed for two years, what is the probability that the machine you purchased will require replacement under guarantee?


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potomatos

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Reply #1 on: Jul 24, 2018
Answer to Question 1

The area to the left of z is 0.005, hence z = -2.58 . Then, -2.58 = (x  6.2) / 1.4 . Solving for x, we get x = (-2.58)(1.4) + 6.2 = 2.588 years.

Answer to Question 2

P(x < 2) = P(z < -3.0) = 0.5000  0.4987 = 0.0013


cdr_15

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Reply 2 on: Jul 24, 2018
Great answer, keep it coming :)

alvinum

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Reply 3 on: Yesterday
YES! Correct, THANKS for helping me on my review

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