SOLUTION: The hard drive reader head is the only likely component to fail, and all that fail are replaced. These have life expectancy that follows a normal distribution with mean 60 months

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Question 855162: The hard drive reader head is the only likely component to fail, and all that fail are replaced. These have life expectancy that follows a normal distribution with mean 60 months and standard deviation of 2 months. what is the longest time that the manufacturer can guarantee the hard drives if they want to replace no more than 4% of them?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The hard drive reader head is the only likely component to fail, and all that fail are replaced. These have life expectancy that follows a normal distribution with mean 60 months and standard deviation of 2 months. what is the longest time that the manufacturer can guarantee the hard drives if they want to replace no more than 4% of them?
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Find the z-value with a left-tail of 4%:: invNorm(0.04) = -1.7507
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Find the corresponding time.
x = z*s+u
x = -1.7507*2+60 = 56.49
Ans:: 56 months
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Cheers,
Stan H.