Question 722362: Swift Auto Service has taken advantage of some of the results
you provided (HW #4) and has improved their process. Their oil &
lube “service time per car” still follows a normal distribution, but
now with a mean of 30 minutes per car, and a standard deviation
of 4.0 minutes.
c) how large would your random sample need to be, so that your
sample mean “service time” would be 99% likely to be within
1 minute of the true population mean service time ?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Swift Auto Service has taken advantage of some of the results
you provided (HW #4) and has improved their process. Their oil &
lube “service time per car” still follows a normal distribution, but
now with a mean of 30 minutes per car, and a standard deviation
of 4.0 minutes.
c) how large would your random sample need to be, so that your
sample mean “service time” would be 99% likely to be within
1 minute of the true population mean service time ?
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Since E = z*s/sqrt(n),
n = [z*s/E]^2 = [2.5758*4/1]^2 = 106 when rounded down
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Cheers,
Stan H.
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