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

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) (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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