# a study of nickels showed that the standard deviation of the weight of nickels is 150 milligrams. a coin counter manufacterer 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 20 milligrams

Question

a study of nickels showed that the standard deviation of the weight of nickels is 150 milligrams. a coin counter manufacterer 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 20 milligrams