document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=807552>Question 807552</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A group of investors wants to develop a chain of fast-food restaurants. In determining potential costs for each facility, they must consider, among other expenses, the average monthly electric bill. They decide to sample some fast-food restaurants currently operating to estimate the monthly cost of<BR>\n" );
document.write( "electricity. They want to be 90% confident of their results and want the error of the interval estimate to be no more than $100. They estimate that such bills range from $600 to $2,500. How large a sample should they take? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #486356 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=486356\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A group of investors wants to develop a chain of fast-food restaurants. In determining potential costs for each facility, they must consider, among other expenses, the average monthly electric bill. They decide to sample some fast-food restaurants currently operating to estimate the monthly cost of<BR>\n" );
document.write( "electricity. They want to be 90% confident of their results and want the error of the interval estimate to be no more than $100. They estimate that such bills range from $600 to $2,500. How large a sample should they take?<BR>\n" );
document.write( "------<BR>\n" );
document.write( "Using the 6-sigma estimate for the standard deviation:<BR>\n" );
document.write( "6s = (2500-600)<BR>\n" );
document.write( "s = 1900/6<BR>\n" );
document.write( "s = 316.67<BR>\n" );
document.write( "==========<BR>\n" );
document.write( "Formula:<BR>\n" );
document.write( "n = [z*s/E]^2<BR>\n" );
document.write( "n = [1.645*316.67/100]^2<BR>\n" );
document.write( "n = 28 when rounded up<BR>\n" );
document.write( "=============================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "============================= </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );