document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1182660>Question 1182660</A>: <I><SPAN STYLE=\"word-break: break-all;\"> You want to obtain a sample to estimate a population mean.<BR>\n" );
document.write( "Based on previous evidence, you believe the population standard deviation is approximately =39.5.<BR>\n" );
document.write( "You would like to be 90% confident that your estimate is within 10 of the true population mean.<BR>\n" );
document.write( "How large of a sample size is required?<BR>\n" );
document.write( "Do not round mid-calculation.\r<BR>\n" );
document.write( "\n" );
document.write( "n= </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #812771 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=812771\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> for 90% CI; error=z(0.95)*sigma/sqrt(n)<BR>\n" );
document.write( "10=1.645*39.5/sqrt(n); square both sides<BR>\n" );
document.write( "100=2.706*1560.25/n<BR>\n" );
document.write( "n=42.22 round to 43. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );