SOLUTION: A study of nickels showed that the the standard deviation of the weight of nickels is 200 milligrams. A coin counter manufacturer wishes to find the 90% confidence interval for the

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Question 1042155: A study of nickels showed that the the standard deviation of the weight of nickels is 200 milligrams. A coin counter manufacturer wishes to find the 90% confidence interval for the average weight of a nickel. How many nickels does he need to weigh to obtain an average accurate to within 20 milligrams?
A.
100
B.
164
C.
273
D.
385
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A study of nickels showed that the the standard deviation of the weight of nickels is 200 milligrams. A coin counter manufacturer wishes to find the 90% confidence interval for the average weight of a nickel. How many nickels does he need to weigh to obtain an average accurate to within 20 milligrams?
A.
100
B.
164
C.
273
D.
385
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n = [z*s/E]^2 = [1.645*200/20]^2 = 16.45^2 = 271 when rounded up
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Cheers,
Stan H.
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