document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=836188>Question 836188</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An advertising agency wishes to estimate the proportion of households which use a particular brand of flour.  i) They decide on a sample size of 500, and find that 157 households use the products. Construct a 99% confidence interval for the proportion of households. ii) How large should the sample have been for their estimate to have been in error by less than 2%? <BR>\n" );
document.write( " (2+3 = 5 marks)  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #504019 by </B><A HREF=/tutors/aboutme.mpl?userid=psbhowmick><B>psbhowmick(878)</B></A><img src=\"/images/stars/stars-11.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=psbhowmick><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/cgi-bin/show-face.mpl?user=psbhowmick><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=504019\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> ii) The sample size can be estimated by:\r<BR>\n" );
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document.write( "N=(Z*p(1-p))/(ME)^2\r<BR>\n" );
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document.write( "p = 157/500 = 0.314\r<BR>\n" );
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document.write( "N = (2.34*0.314*0.686)/(0.02)^2 = 1260.1\r<BR>\n" );
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document.write( "Required sample size = 1261. </SPAN>\n" );
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