document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1062249>Question 1062249</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A survey indicated that 78% of secondary students graduate within five years of entering grade 9. This result is considered accurate with plus/minus 3%, 19 of 20 times. Estimate the sample size of this survey. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #677145 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=677145\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The error at the 5% level is equal to z(0.975)*sqrt (p*(1-p))/n=0.03<BR>\n" );
document.write( "square both sides; z=1.96<BR>\n" );
document.write( "3.8416*0.78*0.22/n=0.0009<BR>\n" );
document.write( "0.6592=0.0009n<BR>\n" );
document.write( "n=732.46 or 733.<BR>\n" );
document.write( "Check:<BR>\n" );
document.write( "A rough guide at the 95% level is the error is 1/sqrt (n)=1/sqrt (733)=0.0369.<BR>\n" );
document.write( "This guideline is accurate when z=2 and p=1-p=0.5.  Nevertheless, this is a good check. </SPAN>\n" );
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