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(a) Construct a 95 percent confidence interval for the true mean.
(b) Why might normality be an issue here?
(c) What sample size would be needed to obtain an error of ±10 square millimeters with 99 percent confidence?
(d) If this is not a reasonable requirement, suggest one that is.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 260
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Hopefully you can find the mean (x-bar) and the
standard deviation (s), which is needed to
calculate the standard error (E).
Do that first then attack the questions below.
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(a) Construct a 95 percent confidence interval for the true mean.
x-bar-E < u < x-bar+E
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(b) Why might normality be an issue here?
I'll leave that to you.
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(c) What sample size would be needed to obtain an error of ±10 square millimeters with 99 percent confidence?
Since E = zs/sqrt(n)
sqrt(n) = zs/E
then n = [zs/E]^2
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For a 95% C.I., z = 1.96
You have figured out the sample standard deviation
You are told that E = 10
So n = [1.96*s/10]^2
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(d) If this is not a reasonable requirement, suggest one that is.
If "n" seems too large you could reduce the confidence requirement,
or increase the size of the error limit.
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Get back to me if you need further help.
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Cheers,
Stan H.
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