document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=129780>Question 129780</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please,I really need some help with this problem:\r<BR>\n" );
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document.write( "The manufacturer of Winston Tire Company (WTC) claims its new tires last for an average 45k miles. An independent testing agency road-tested 135 tires to substantiate the claim made by WTC. The sample mean was 44k miles with a sample standard deviation of 4k miles. Using 1% significance, determine if there is a reason to reject the claim made by WTC and conclude that the tires last for less than 45k miles.<BR>\n" );
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document.write( "Lets do this in an interactive fashion.<BR>\n" );
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document.write( "First, answer the following questions:<BR>\n" );
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document.write( "- what is 'n'<BR>\n" );
document.write( "- calculate the confidence intervals (using 44k miles as your mean) (1% significance means 99% confidence)\r<BR>\n" );
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document.write( "Thanks... </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #94783 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=94783\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The manufacturer of Winston Tire Company (WTC) claims its new tires last for an average 45k miles. An independent testing agency road-tested 135 tires to substantiate the claim made by WTC. The sample mean was 44k miles with a sample standard deviation of 4k miles. Using 1% significance, determine if there is a reason to reject the claim made by WTC and conclude that the tires last for less than 45k miles.<BR>\n" );
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document.write( "- what is 'n'<BR>\n" );
document.write( "Ans: n is the sample size; in your problem that would be 135<BR>\n" );
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document.write( "- calculate the confidence intervals (using 44k miles as your mean) (1% significance means 99% confidence) <BR>\n" );
document.write( "Ans: The standard error is E= 2.575(4/sqrt(135)) = 7.48..<BR>\n" );
document.write( "C.I. is (44-E,44+E)<BR>\n" );
document.write( "C.I. is (36.52,51.48)<BR>\n" );
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document.write( "Fail to reject the claim since 45K is in the 1% confidence interval.<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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