document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=188256>Question 188256</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0072966939/algebrahomeworkh>Applied Statistics in Business and Economics</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area devoted to display ads was measured (a display ad is a large block of multicolored illustrations, maps, and text). The data (in square millimeters) are shown below:\r<BR>\n" );
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document.write( "0 	260 	356 	403 	536 	0 	268 	369 	428 	536<BR>\n" );
document.write( "268 	396 	469 	536 	162 	338 	403 	536 	536 	130\r<BR>\n" );
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document.write( "(a) Construct a 95 percent confidence interval for the true mean. <BR>\n" );
document.write( "(b) Why might normality be an issue here? <BR>\n" );
document.write( "(c) 	What sample size would be needed to obtain an error of ±10 square millimeters with 99 percent confidence? <BR>\n" );
document.write( "(d) If this is not a reasonable requirement, suggest one that is. <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 #141136 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=141136\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area devoted to display ads was measured (a display ad is a large block of multicolored illustrations, maps, and text). The data (in square millimeters) are shown below: <BR>\n" );
document.write( "0 260 356 403 536 0 268 369 428 536<BR>\n" );
document.write( "268 396 469 536 162 338 403 536 536 130 <BR>\n" );
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document.write( "The sample mean is 346.5<BR>\n" );
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document.write( "(a) Construct a 95 percent confidence interval for the true mean.<BR>\n" );
document.write( "E = 1.96 = 74.6716<BR>\n" );
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document.write( "95% C.I.: 346.5 - 74.6716 < u < 346.5 + 74.6716<BR>\n" );
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document.write( "(b) Why might normality be an issue here?<BR>\n" );
document.write( "I'll leave that to you.<BR>\n" );
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document.write( "(c) What sample size would be needed to obtain an error of ±10 square<BR>\n" );
document.write( " millimeters with 99 percent confidence?<BR>\n" );
document.write( "E = z<BR>\n" );
document.write( "n = [z*s/E]^2<BR>\n" );
document.write( "n = [1.96*170.38/10]^2 = 1115 <BR>\n" );
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document.write( "(d) If this is not a reasonable requirement, suggest one that is.<BR>\n" );
document.write( "Increase the error-limit requirement and/or reduce the confidence limit.<BR>\n" );
document.write( "===========================================================================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. <BR>\n" );
document.write( " </SPAN>\n" );
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