document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=359163>Question 359163</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Families USA, a monthly magazine that discusses issues related to health and health costs, surveyed 20 of its subscribers. It found that the annual health insurance premiums for a family with coverage through an employer averaged $10,979. The standard deviation of the sample was $1,000.\r<BR>\n" );
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document.write( "a. Based on this sample information, develop a 90 percent confidence interval for the<BR>\n" );
document.write( "population mean yearly premium.\r<BR>\n" );
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document.write( "b. How large a sample is needed to find the population mean within $250 at 99 percent<BR>\n" );
document.write( "confidence?<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 #256397 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=256397\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Families USA, a monthly magazine that discusses issues related to health and health costs, surveyed 20 of its subscribers. It found that the annual health insurance premiums for a family with coverage through an employer averaged $10,979. The standard deviation of the sample was $1,000. <BR>\n" );
document.write( "a. Based on this sample information, develop a 90 percent confidence interval for the population mean yearly premium.<BR>\n" );
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document.write( "x-bar = 10979<BR>\n" );
document.write( "ME = 1.645*1000/sqrt(20) = 367.83<BR>\n" );
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document.write( "90% CI: 10979-367.82 < u < 10979+367.83<BR>\n" );
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document.write( "b. How large a sample is needed to find the population mean within $250 at 99 percent confidence?<BR>\n" );
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document.write( "n = [zs/E]^2 = [2.5758*1000/250]^2 = 107 when rounded up<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.\r<BR>\n" );
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