document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1173009>Question 1173009</A>: <I><SPAN STYLE=\"word-break: break-all;\"> it is claimed that people drive on the average 18.000 km per year. A consumer form believes that the average mileage is probably lower. to check, the consumer firm abtained information from 40 randomly selected car owners that resulted in a sample mean of 17, 463 km with a sample standard deviation of 1348 km what can we conclude about this claim? use alpha </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #798169 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=798169\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> claim is 18,000 km per year.\r<BR>\n" );
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document.write( "sample of 40 randomly selected car owners results in a sample mean of 17,463 km with a sample standard deviation of 1348 km.\r<BR>\n" );
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document.write( "standard error = standard deviation of sample divided by square root of sample size = 1348 / sqrt(40) = 213.375143\r<BR>\n" );
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document.write( "since the standard deviation is taken from the sample, then you use t-score.\r<BR>\n" );
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document.write( "t-score = (x - m) / s<BR>\n" );
document.write( "x is the raw score<BR>\n" );
document.write( "m is the mean<BR>\n" );
document.write( "s is the standard error.\r<BR>\n" );
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document.write( "you get:<BR>\n" );
document.write( "t-score = (17,463 - 18,000) / 213.375143 = -2.515584261.\r<BR>\n" );
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document.write( "area to the left of that under the normal distribution curve is equal to .0080345273.\r<BR>\n" );
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document.write( "at 99% confidence level, the area to the left is less than .01.<BR>\n" );
document.write( "this means the results are significant.\r<BR>\n" );
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document.write( "this means that the claim that the average mileage is probably lower is valid at the 99% confidence level.\r<BR>\n" );
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document.write( "with t-score, you need to use degrees of freedom.<BR>\n" );
document.write( "with a sample size of 40, the degrees of freedom is 39.\r<BR>\n" );
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document.write( "i used the ti-84 plus to solve for the area to the left of the indicated z-score.\r<BR>\n" );
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document.write( "an online calculator that does the same can be found at <a  rel=nofollow HREF= \"https://stattrek.com/online-calculator/t-distribution.aspx\" target = \"_blank\">https://stattrek.com/online-calculator/t-distribution.aspx</a>\r<BR>\n" );
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document.write( "it provided the same answer rounded to 4 decimal places.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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