SOLUTION: As estimate of the mean time of continuous use until an answering machine will first require service is desired. If it can be assumed that α = 60 days, how large a sample i

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Question 1011521: As estimate of the mean time of continuous use until an
answering machine will first require service is desired. If
it can be assumed that α = 60 days, how large a sample
is needed so that one will be able to assert with 90%
confidence that the sample mean is off by at most 10
days?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
As estimate of the mean time of continuous use until an
answering machine will first require service is desired.
If it can be assumed that α = 60 days, how large a sample
is needed so that one will be able to assert with 90%
confidence that the sample mean is off by at most 10
days?
---
E = z*s/sqrt(n)
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Therefore::
n = [z*s/E]^2
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Your Problem::
n = [1.654*60/10] = 9.924^2 = 99 when rounded up
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Cheers,
Stan H.
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