document.write( "Question 415739: \In a scan of a number of books in the college bookstore, you have discovered that it has books that are new and books that are up to ten years old. How many books must you review to estimate the mean age (in years) of all the books in the bookstore? Assume a 96% degree of confidence that the sample mean will be in error by no more than 0.25 year. \n" ); document.write( "
Algebra.Com's Answer #291405 by stanbon(75887)\"\" \"About 
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\In a scan of a number of books in the college bookstore, you have discovered that it has books that are new and books that are up to ten years old. How many books must you review to estimate the mean age (in years) of all the books in the bookstore? Assume a 96% degree of confidence that the sample mean will be in error by no more than 0.25 year.
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\n" ); document.write( "n = [zs/E]^2
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\n" ); document.write( "n = [2.0537*s/0.25]^2
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\n" ); document.write( "To estimate \"s\": The age range is 0 to 10
\n" ); document.write( "Let 6*sigma = 10
\n" ); document.write( "Then sigma = 5/3
\n" ); document.write( "Use that for \"s\".
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\n" ); document.write( "n = [2.0536*(5/3)/0.25]^2 = 187.46
\n" ); document.write( "Rounding up you get n = 188
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\n" ); document.write( "cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "
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