document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1091933>Question 1091933</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A population is estimated to have a standard deviation of 11. We want to estimate the population mean within 3, with a 90% level of confidence. (Use  z Distribution Table.)<BR>\n" );
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document.write( "How large a sample is required? (Round the z-values to 2 decimal places. Round up your answer to the next whole number.)<BR>\n" );
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document.write( "  Sample required is ____?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #706445 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=706445\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> We use the following formula to solve this problem<BR>\n" );
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document.write( "E = z(a/2) * (s/square root(n)), where<BR>\n" );
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document.write( "E is the required difference between the sample mean and the population mean<BR>\n" );
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document.write( "z(a/2) is the positive z value for a(alpha)/2<BR>\n" );
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document.write( "s is the standard deviation of the population<BR>\n" );
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document.write( "n is the number for the sample size<BR>\n" );
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document.write( "n = ( z(a/2) * s / E )^2<BR>\n" );
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document.write( "a = 1 - (90/100) = 0.10<BR>\n" );
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document.write( "z(0.05) = 1.65<BR>\n" );
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document.write( "n = ( 1.65 * 11 / 3)^2 = 36.6025<BR>\n" );
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document.write( "the sample required is 37<BR>\n" );
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