Question 825783: The lifetime of a certain type of machine is normally distributed with mean=2.5 years, and standard deviation=1.4 years. If this type of machine is guaranteed for 1 year, approxiametly what fraction of original sales will require replacement?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! The lifetime of a certain type of machine is normally distributed with mean=2.5 years, and standard deviation=1.4 years. If this type of machine is guaranteed for 1 year, approxiametly what fraction of original sales will require replacement?
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z(1) = (1-2.5)/1.4 = -1.07
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P(x < 1) = P(z < -1.07)
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Comment: Use a z-chart, software,
or calculator to find the area under
the normal curve to the left of z = -1.07
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I use a TI-84 calculator to get the following::
P(z < -1.07) = normalcdf(-100,-1.07) = 0.1423
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Ans: 1423/10,000
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Cheers,
Stan H
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