document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=353762>Question 353762</A>: <I><SPAN STYLE=\"word-break: break-all;\"> You are trying to estimate the average amount a family spends on food during a year.  In the past, the standard deviation of the amount a family spends on food during the year has been approximately $1,500<BR>\n" );
document.write( "a.	If you want to be 95% sure that you have estimated average family food expenditures within $100, how many families do you need to survey?<BR>\n" );
document.write( "b.	How many do you need to survey if you want to be 99% sure?<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 #252878 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=252878\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> You are trying to estimate the average amount a family spends on food during a year.  In the past, the standard deviation of the amount a family spends on food during the year has been approximately $1,500<BR>\n" );
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document.write( "a.	If you want to be 95% sure that you have estimated average family food expenditures within $100, how many families do you need to survey?<BR>\n" );
document.write( "Since E = zs/sqrt(n)<BR>\n" );
document.write( "n = [zs/E]^2<BR>\n" );
document.write( "n = [1.96*1500/100]^2 = 865 when rounded up<BR>\n" );
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document.write( "b.	How many do you need to survey if you want to be 99% sure?<BR>\n" );
document.write( "n = [2.5758*1500/100]^2 = 1493 when rounded up<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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