document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1058050>Question 1058050</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Testing the variance \r<BR>\n" );
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document.write( "Suppose an airline claims that its flights are consistently<BR>\n" );
document.write( "on time with an average delay of at most 15 minutes. It claims that the average delay is so consistent that the variance is no<BR>\n" );
document.write( "more than 150 minutes. Doubting the consistency part of the claim, a disgruntled traveler calculates the delays for his next<BR>\n" );
document.write( "25 flights. The average delay for those 25 flights is 22 minutes with a standard deviation of 15 minutes.\r<BR>\n" );
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document.write( " My questions below\r<BR>\n" );
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document.write( "what is the df=_______ ?\r<BR>\n" );
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document.write( "Let a= 0.05<BR>\n" );
document.write( "Decision ________<BR>\n" );
document.write( "Conclusion write out in complete sentence </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #673084 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=673084\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Our Ho is variance = 150 minutes and H1 is variance > 150 minutes<BR>\n" );
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document.write( "degrees of freedom(df) = sample size - 1 = 25 - 1 = 24<BR>\n" );
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document.write( "Note that variance = (standard deviation)^2<BR>\n" );
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document.write( "variance of the sample = 15^2 = 225<BR>\n" );
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document.write( "H1 does not contain an =, therefore we use a one-tailed test<BR>\n" );
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document.write( "Our test statistic is calculated<BR>\n" );
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document.write( "c = ((25 - 1) * 225) / 150 = 36<BR>\n" );
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document.write( "alpha(a) = 0.05<BR>\n" );
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document.write( "we check the chi-square distribution table<BR>\n" );
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document.write( "df of 24 and a = 0.05 gives us a probability value(p-value) of 0.0549<BR>\n" );
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document.write( "since our p-value > 0.05, there is no reason to reject our null hypothesis(Ho)<BR>\n" );
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