document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1169774>Question 1169774</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A manufacturer claims that the mean lifetime, u of its light bulbs is 43 months. the standard deviation of these lifetimes is 9 months. eighty light bulbs are selected at random, and their mean lifetime is found to be 40 months. can we conclude, at the 0.01 level of significance, that the mean lifetime of light bulbs made by this manufacturer differs from 43 months? <BR>\n" );
document.write( "Perform a two tail test. then fill in the table below.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #794600 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=794600\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Ho: outcomes are the same<BR>\n" );
document.write( "Ha: they are not<BR>\n" );
document.write( "alpha p{reject Ho|Ho true}=0.01<BR>\n" );
document.write( "test is a z 0.995, <BR>\n" );
document.write( "critical value is |z|>2.576<BR>\n" );
document.write( "calculation z=(40-43)/9/sqrt(80)<BR>\n" );
document.write( "z=-3sqrt(80)/9<BR>\n" );
document.write( "=2.98<BR>\n" );
document.write( "reject Ho p-value 0.0029 The mean lifetime of the light bulbs differs from 43 months. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );