document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=194063>Question 194063</A>: <I><SPAN STYLE=\"word-break: break-all;\"> My company has a fleet of 700 buses and 140 rail cars for urban mass transit <BR>\n" );
document.write( "We repair everything ourselves.  Recently we decided to try a Lean Manufacturing approach and try to optimize a standard engine rebuild that we do.<BR>\n" );
document.write( "Our history data on the rebuild ( Same engine in all cases ) population mean was 34 hours with a 8 hour standard deviation.<BR>\n" );
document.write( "After applying lean manufacturing principles on our rebuild team, we waited a few weeks for the \"new\" way to settle in then we retested to see if the times changed statistically<BR>\n" );
document.write( "We sampled 30 jobs randomly and found a sample mean of 31 hours <BR>\n" );
document.write( "Test at the 0.05 alpha, 2 tail test to see if we made statistical improvement 0.05 = 1.96 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #145659 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=145659\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> My company has a fleet of 700 buses and 140 rail cars for urban mass transit <BR>\n" );
document.write( "We repair everything ourselves. Recently we decided to try a Lean Manufacturing approach and try to optimize a standard engine rebuild that we do.<BR>\n" );
document.write( "Our history data on the rebuild ( Same engine in all cases ) population mean was 34 hours with a 8 hour standard deviation.<BR>\n" );
document.write( "After applying lean manufacturing principles on our rebuild team, we waited a few weeks for the \"new\" way to settle in then we retested to see if the times changed statistically<BR>\n" );
document.write( "We sampled 30 jobs randomly and found a sample mean of 31 hours <BR>\n" );
document.write( "Test at the 0.05 alpha, 2 tail test to see if we made statistical improvement 0.05 = 1.96<BR>\n" );
document.write( "---------------<BR>\n" );
document.write( "Ho: u(old method) - u(new method) = 0<BR>\n" );
document.write( "H1: u(old method) - u(new method) > 0<BR>\n" );
document.write( "-----------------<BR>\n" );
document.write( "t(34-31) = 3/sqrt[(8^2/840 + ?^2/30)] = ?<BR>\n" );
document.write( "----------------------------------------------<BR>\n" );
document.write( "Comment: You did not post the standard deviation of the sample of 30.<BR>\n" );
document.write( "------------------------------------------------<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );