document.write( "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?
\n" ); document.write( " A.
\n" ); document.write( "100
\n" ); document.write( " B.
\n" ); document.write( "164
\n" ); document.write( " C.
\n" ); document.write( "273
\n" ); document.write( " D.
\n" ); document.write( "385
\n" ); document.write( " \n" ); document.write( "
Algebra.Com's Answer #657116 by stanbon(75887)\"\" \"About 
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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?
\n" ); document.write( "A.
\n" ); document.write( "100
\n" ); document.write( "B.
\n" ); document.write( "164
\n" ); document.write( "C.
\n" ); document.write( "273
\n" ); document.write( "D.
\n" ); document.write( "385
\n" ); document.write( "------------
\n" ); document.write( "n = [z*s/E]^2 = [1.645*200/20]^2 = 16.45^2 = 271 when rounded up
\n" ); document.write( "-------------
\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
\n" ); document.write( "------------- \n" ); document.write( "
\n" );