document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1086581>Question 1086581</A>: <I><SPAN STYLE=\"word-break: break-all;\"> You are estimating the cost of engine overhauls. A sample of 49 repairs showed an average overhaul of 285 hours with a standard deviation of 60 hours. Calculate a 95% confidence interval for the average overhaul. (Carry intermediate calculations to three decimal places.)\r<BR>\n" );
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document.write( "   a. 271.00 &#8804; &#956; &#8804; 299.00 <BR>\n" );
document.write( "   b. 268.20 &#8804; &#956; &#8804; 301.80 <BR>\n" );
document.write( "   c. 281.61 &#8804; &#956; &#8804; 288.39 <BR>\n" );
document.write( "   d. 284.52 &#8804; &#956; &#8804; 285.48 \r<BR>\n" );
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document.write( "You are estimating the cost of a personnel shelter and you have collected cost data on 10 shelters. The mean cost was $16,693. The median cost is $17,402. There is a range in the cost of $10,095. The standard deviation is $2,270. If you use the average cost of the shelters as your estimate, then, on average:\r<BR>\n" );
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document.write( "   a. You could expect to be off by $10,095. <BR>\n" );
document.write( "   b. You could expect to be off by 20.42%. <BR>\n" );
document.write( "   c. You could expect to be off by 13.60%. <BR>\n" );
document.write( "   d. You could expect to be off by $340.90. <BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #700854 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=700854\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <font color=\"black\" face=\"times\" size=\"3\">I'll do the first one to get you started\r<BR>\n" );
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document.write( "z = 1.960 (z critical value at 95% confidence)<BR>\n" );
document.write( "n = 49<BR>\n" );
document.write( "xbar = 285<BR>\n" );
document.write( "s = 60\r<BR>\n" );
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document.write( "The lower limit of the confidence interval is<BR>\n" );
document.write( "L = xbar - z*(s/sqrt(n))<BR>\n" );
document.write( "L = 285 - 1.96*(60/sqrt(49))<BR>\n" );
document.write( "L = 285 - 1.96*(60/7)<BR>\n" );
document.write( "L = 285 - 1.96*(8.57142857142857)<BR>\n" );
document.write( "L = 285 - 16.8<BR>\n" );
document.write( "L = 268.2\r<BR>\n" );
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document.write( "The upper limit of the confidence interval is<BR>\n" );
document.write( "U = xbar + z*(s/sqrt(n))<BR>\n" );
document.write( "U = 285 + 1.96*(60/sqrt(49))<BR>\n" );
document.write( "U = 285 + 1.96*(60/7)<BR>\n" );
document.write( "U = 285 + 1.96*(8.57142857142857)<BR>\n" );
document.write( "U = 285 + 16.8<BR>\n" );
document.write( "U = 301.8\r<BR>\n" );
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document.write( "(L,U) = (268.2,301.8)\r<BR>\n" );
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document.write( "The final answer is <font color=red>choice B) 268.20 < µ < 301.80</font><BR>\n" );
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