document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1065076>Question 1065076</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If nine software engineers were interviewed to develop an estimate for software lines of code.   The mean estimate is 12480 lines of code with a standard deviation of 2000 lines of code.  Develop a 90 per cent confidence interval for the population mean.  Carry to three decimal places\r<BR>\n" );
document.write( "\n" );
document.write( "Would the correct answer be 10992 13968 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #680230 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=680230\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The sample mean is 12480 and the sample standard deviation is 2000<BR>\n" );
document.write( ":<BR>\n" );
document.write( "We want a 90% confidence interval for the population mean<BR>\n" );
document.write( ":<BR>\n" );
document.write( "alpha(a) is 1 - (90/100) = 0.10<BR>\n" );
document.write( ":<BR>\n" );
document.write( "critical probability(p*) = 1 - (a/2) = 0.95<BR>\n" );
document.write( ":<BR>\n" );
document.write( "because our sample size is < 30, we use the t-statistic<BR>\n" );
document.write( ":<BR>\n" );
document.write( "degrees of freedom = 9 - 1 = 8<BR>\n" );
document.write( ":<BR>\n" );
document.write( "we lookup in the students t-table the critical value(CV) that has 8 degrees of freedom and a p* of 0.95<BR>\n" );
document.write( ":<BR>\n" );
document.write( "CV is 1.860<BR>\n" );
document.write( ":<BR>\n" );
document.write( "margin of error(ME) = CV * standard deviation = 1.860 * 2000 = 3720<BR>\n" );
document.write( ":<BR>\n" );
document.write( "***********************************************************<BR>\n" );
document.write( "95% confidence interval = 12480 + or - 3720 = (8760, 16200)<BR>\n" );
document.write( "***********************************************************<BR>\n" );
document.write( ":<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );