SOLUTION: A previous analysis of paper boxes showed that the standard deviation of their lengths is 15 millimeters. A packer wishes to find the 90% confidence interval for the average lengt

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Question 593061: A previous analysis of paper boxes showed that the standard deviation of their
lengths is 15 millimeters. A packer wishes to find the 90% confidence interval for the average length of a box. How many boxes does he need to measure to be accurate within 3 millimeters?
A) 25 B) 97 C) 69 D) 41
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A previous analysis of paper boxes showed that the standard deviation of their
lengths is 15 millimeters. A packer wishes to find the 90% confidence interval for the average length of a box. How many boxes does he need to measure to be accurate within 3 millimeters?
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n = [z*s/E]^2
n = [1.645*15/3]^2 = 68 when rounded up.
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Cheers,
Stan H.
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A) 25 B) 97 C) 69 D) 41