document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1119834>Question 1119834</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The level of nitrogen oxides (NOX) in the exhaust of a particular car model varies with mean 0.9 grams per mile and standard deviation 0.2 grams per mile .\r<BR>\n" );
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document.write( "(a) What sample size is needed so that the standard deviation of the sampling distribution is 0.01 grams per mile ?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #735495 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=735495\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> mean = .9\r<BR>\n" );
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document.write( "standard deviation = .2\r<BR>\n" );
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document.write( "standard error = standard deviation of sampling distribution.\r<BR>\n" );
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document.write( "formula for that is s = standard deviation / square root of sample size.\r<BR>\n" );
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document.write( "to make s = .01, the formula becomes .01 = .2 / sqrt(n)\r<BR>\n" );
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document.write( "n is the sample size.\r<BR>\n" );
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document.write( "multiply both sides of this equation by sqrt(n) and divide both sides of this equation by .01 to get:\r<BR>\n" );
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document.write( "sqrt(n) = .2 / .01.\r<BR>\n" );
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document.write( "solve for sqrt(n) to get sqrt(n) = 20\r<BR>\n" );
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document.write( "solve for n to get n = 20^1 = 400.\r<BR>\n" );
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document.write( "when n = 400, the standard error will be .2 / sqrt(400) = .2 / 20 = .01.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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