document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1159165>Question 1159165</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A shipping firm suspects that the mean life of a certain brand of tire used by its trucks is more than 40,000 miles. To check the claim, the firm randomly selects and tests 18 of these tires and gets a mean lifetime of 40503 miles with a standard deviation of 1200 miles. At α = 0.05, test the shipping firm's claim. Assume the distribution is normal. Use the P-value method. Exact value of the standard deviation is not known.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #782516 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=782516\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> this is a t-test (last statement)<BR>\n" );
document.write( "Ho: brand lasts < 40000 miles<BR>\n" );
document.write( "Ha: it lasts more<BR>\n" );
document.write( "alpha=0.05 P{reject Ho|Ho true|<BR>\n" );
document.write( "test statistic is a t 0.95, df=17<BR>\n" );
document.write( "critical value is t> 1.74 for a one way test<BR>\n" );
document.write( "calculation t=(x bar- mean)/s/sqrt(n)<BR>\n" );
document.write( "=503*sqrt(18)/1200<BR>\n" );
document.write( "=1.78<BR>\n" );
document.write( "because t >1.74, can conclude the tires do last for more than 40,000 miles<BR>\n" );
document.write( "p=0.0466 </SPAN>\n" );
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