document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=137843>Question 137843</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am having a lot of trouble with a couple of questions. Can someone please explain and help me with them?\r<BR>\n" );
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document.write( "1) What is the 90% confidence interval for the variance of exam scores for 28 algebra students, if the standard deviation of their last exam is 12.7?\r<BR>\n" );
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document.write( "A) 108.6<a^2<269.6<BR>\n" );
document.write( "B) 10.4<a^2<16.4<BR>\n" );
document.write( "C) 123.7<a^2<312.7<BR>\n" );
document.write( "D) 122.8<a^2<316.5\r<BR>\n" );
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document.write( "2) A sample of 23 European countries found the variance on life expectancy was 7.3 years. What is the 95% confidence interval for the variance of life expectancy in Europe?\r<BR>\n" );
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document.write( "A) 27.2<a^2<118.3<BR>\n" );
document.write( "B) 5.6<a^2<10.3<BR>\n" );
document.write( "C) 4.4<a^2<14.6<BR>\n" );
document.write( "D) 28.9<a^2<115.0\r<BR>\n" );
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document.write( "Thank you for your help.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #100770 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=100770\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 1) What is the 90% confidence interval for the variance of exam scores for 28 algebra students, if the standard deviation of their last exam is 12.7? <BR>\n" );
document.write( "A) 108.6 B) 10.4 C) 123.7 D) 122.8 \r<BR>\n" );
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document.write( "(28-1)(12.7)^2/43.194 < sigma^2 < (28-1)(12.7)^2 /14.573\r<BR>\n" );
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document.write( "100.827... < sigma^2 < 298.83<BR>\n" );
document.write( "Comment: The answers you are given are for the 90% confidence interval<BR>\n" );
document.write( "lower limit for the standard deviation.  If you take the square root of <BR>\n" );
document.write( "the lower limit for sigma^2 you get 10.04 which is answer B.<BR>\n" );
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document.write( "2) A sample of 23 European countries found the variance on life expectancy was 7.3 years. What is the 95% confidence interval for the variance of life expectancy in Europe? <BR>\n" );
document.write( "A) 27.2 B) 5.6 C) 4.4 D) 28.9 \r<BR>\n" );
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document.write( "(23-1)7.3/36.781 < sigma^2 < (23-1)7.3/10.982\r<BR>\n" );
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document.write( "4.3664  < sigma2  < 14.624<BR>\n" );
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document.write( "I have no idea what your A,B,C,D answers might mean.<BR>\n" );
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document.write( "The formula I am using is as follows:\r<BR>\n" );
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document.write( "[(n-1)s^2/(Ch-Sq Right)] < sigma^2 < [(n-1)s^2/Ch-Sq Left)]<BR>\n" );
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document.write( "cheers,<BR>\n" );
document.write( "Stan H.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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