document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1131643>Question 1131643</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A trainer wants to estimate the population mean training time for female runners within 2 minutes. Determine the minimum sample size required to construct a 99% confidence interval for the population mean training time of female runners. Assume the population standard deviation is 8.4 minutes.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #748891 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=748891\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> this is a z-test since sd known<BR>\n" );
document.write( "99% CI z for two sided is 2.576<BR>\n" );
document.write( "half-interval is z*sigma/sqrt(n)=2<BR>\n" );
document.write( "square both sides<BR>\n" );
document.write( "z^2*sigma^2/n=4<BR>\n" );
document.write( "n=z^2*sigma^2/4=117.05 or 118 ANSWER<BR>\n" );
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