document.write( "Question 899073: The National Climate Data Center reports that the mean annual heating degree-days for the period 1949–2006 was 4500 with a standard deviation of 200. Assume that the shape of the data distribution is not known.
\n" ); document.write( "At least ___ percent of years have heating degree-days between 4100 and 4900. \n" ); document.write( "

Algebra.Com's Answer #545175 by ewatrrr(24785) $\"\"$ $\"About$

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z[4900] = (4900 - 4500)/200 = 2
\n" ); document.write( "z(4100) = (4100-4500) /200 = -2
\n" ); document.write( "two standard deviations from the mean account for about 95% \n" ); document.write( "

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