document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=135787>Question 135787</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A careful count of 13,789 carcasses of bugs killed by “mosquito zappers” used in homes near water showed that only 18 were mosquitoes. (a) Construct a 90 percent confidence interval for the proportion of all zapped bugs that are mosquitoes. (b) Is a confidence interval really helpful in deciding whether the devices fulfill their purpose? Explain </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #99592 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=99592\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A careful count of 13,789 carcasses of bugs killed by “mosquito zappers” used in homes near water showed that only 18 were mosquitoes.<BR>\n" );
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document.write( "p-hat = 18/13789 = 0.0013..<BR>\n" );
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document.write( "E = 1.645*sqrt[0.0013*0.9987/13789] = 0.0005047633...<BR>\n" );
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document.write( "(a) Construct a 90 percent confidence interval for the proportion of all zapped bugs that are mosquitoes. <BR>\n" );
document.write( "95% CI: p-hat - E < p > p-hat +E<BR>\n" );
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document.write( "(b) Is a confidence interval really helpful in deciding whether the devices fulfill their purpose? Explain<BR>\n" );
document.write( "I'll leave that to you.<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
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