document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1156421>Question 1156421</A>: <I><SPAN STYLE=\"word-break: break-all;\"> We want to obtain a sample to estimate a population mean. Based on previous evidence, researchers believe the population standard deviation is approximately <BR>\n" );
document.write( "σ=48.7. We would like to be 95% confident that the esimate is within 2.5 of the true population mean. How large of a sample size is required? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #779347 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=779347\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> half-interval has to be with 2.5 of the mean.<BR>\n" );
document.write( "so 2.5=z*sigma/sqrt In)<BR>\n" );
document.write( "2.5 sqrt(n)=z*sigma<BR>\n" );
document.write( "n=z^2*sigma^2/2.5^2<BR>\n" );
document.write( "=1457.77 or 1458<BR>\n" );
document.write( " </SPAN>\n" );
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