document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=380538>Question 380538</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please¡ i do really need help¡<BR>\n" );
document.write( "Exercise 2:<BR>\n" );
document.write( "Several drugs are used to treat diabetes. A sales specialist for a leading pharmaceutical company randomly sampled the records of 10 sales districts to estimate the number of new prescriptions that had been written during a particular month for her company’s new diabetes drug. The numbers of new prescriptions were as follows:<BR>\n" );
document.write( "210, 240, 190, 275, 290, 265, 312, 284, 261, 243.<BR>\n" );
document.write( "a)Find a 90% confidence interval for the average number of new prescriptions written for this new drug among all sales district. What are the assumptions?\r<BR>\n" );
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document.write( "b)Calculate the widths of the 95% and 98% confidence intervals\r<BR>\n" );
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document.write( "c)Assuming that the confidence level remains constant, what sample size is needed to reduce by half the margin of error of the confidence interval in part (a)?<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 #270226 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=270226\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 210, 240, 190, 275, 290, 265, 312, 284, 261, 243.<BR>\n" );
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document.write( "sample mean = 257<BR>\n" );
document.write( "sample std = 37.16<BR>\n" );
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document.write( "a)Find a 90% confidence interval for the average number of new prescriptions written for this new drug among all sales district. What are the assumptions?<BR>\n" );
document.write( "E = 1.645*37.16/sqrt(10) = 19.33<BR>\n" );
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document.write( "90% CI: 257-19.33 < u < 257+19.33<BR>\n" );
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document.write( "b)Calculate the widths of the confidence intervals \r<BR>\n" );
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document.write( "for 95% CI:::Use a z-value of 1.96 in place of 1.645<BR>\n" );
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document.write( "for 98% CI::: Usa a z-value of 2.3263<BR>\n" );
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document.write( "c)Assuming that the confidence level remains constant, what sample size is needed to reduce by half the margin of error of the confidence interval <BR>\n" );
document.write( "in part (a)?<BR>\n" );
document.write( "From part (a): E = 1.645*37.16/sqrt(10) = 19.33<BR>\n" );
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document.write( "E/2 = [1.645*37.16/sqrt(10)*(1/2)<BR>\n" );
document.write( "E/2 = [1.645*37.16/sqrt(10*4)<BR>\n" );
document.write( "Sample size needed = 10*4 = 40<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H. \r<BR>\n" );
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