document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1161499>Question 1161499</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A study found that 73% of elementary students buy lunch at school at least once a month. How large a sample would be necessary to estimate the true proportion within 3 percentage points with 95% confidence? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #785062 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=785062\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> then half-interval or margin of error is 0.03=z*sqrt(p*(1-p)/n)<BR>\n" );
document.write( "0.03=1.96*sqrt(0.73*0.27)/n)<BR>\n" );
document.write( "square both sides<BR>\n" );
document.write( "0.0009=3.8416*0.73*0.27/n<BR>\n" );
document.write( "n=841.31 or 842\r<BR>\n" );
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document.write( " </SPAN>\n" );
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