SOLUTION: QUESTION 6 A study of nickels showed that the the standard deviation of the weight of nickels is 300 milligrams. A coin counter manufacturer wishes to find the 95% confidence in

Question 1077162: QUESTION 6
A study of nickels showed that the the standard deviation of the weight of nickels is 300 milligrams. A coin counter manufacturer wishes to find the 95% confidence interval for the average weight of a nickel. How many nickels does he need to weigh to obtain an average accurate to within 25 milligrams?
A.
554
B.
782
C.
393
D.
144

Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
I will use z since the population sd can be assumed to be 300 mg
the interval has to be 25mg
the interval is z*s/sqrt (n)=25=1.96*300/sqrt(n)
25 sqrt (n)=588
square both sides
625 n=345744
n=553.19 or 554, rounding upward.
A.
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