document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1173268>Question 1173268</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 4. Weight of Containers Find the 90% confidence<BR>\n" );
document.write( "interval for the variance and standard deviation for the<BR>\n" );
document.write( "lifetime of disposable camera batteries if a sample of<BR>\n" );
document.write( "16 disposable camera batteries has a standard deviation\r<BR>\n" );
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document.write( "of 2.1 months. Assume the variable is normally<BR>\n" );
document.write( "distributed. Do you feel that the lifetimes of the<BR>\n" );
document.write( "batteries are relatively consistent? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #798504 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=798504\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> this is a ChiSq with df=15<BR>\n" );
document.write( "(n-1)s^2/CSq lower < sigma^2 < (n-1)s^2/ChiSq upper<BR>\n" );
document.write( "from the table, using .05 for the first and 0.95 for the second<BR>\n" );
document.write( "15*4.41/24.996 < sigma^2 < 15*4.41/7.261; the 4.41 is 2.1^2<BR>\n" );
document.write( "2.65 < sigma ^2 < 9.11 which is the 90% CI for the variance<BR>\n" );
document.write( "take the square root of everything to get the 90% CI of the sd<BR>\n" );
document.write( "(1.63, 3.02) units months.<BR>\n" );
document.write( "The last part of the question is opinion and has a good deal to do with the mean life, which isn't stated. </SPAN>\n" );
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