document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1081971>Question 1081971</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A pizza shop owner wishes to find the 95% confidence interval of the true mean cost of a large plain pizza. How large should the sample be if she wishes to be accurate to within $0.13? A previous study showed that the standard deviation of the price was $0.4. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #696066 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=696066\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the margin of error should be +/-0.13, so 0.13=z*s/sqrt(n)<BR>\n" );
document.write( "1.96*s/ sqrt (n)=0.13<BR>\n" );
document.write( "1.96*0.4=0.13* sqrt(n), after multiplying through <BR>\n" );
document.write( "divide through by 0.13 and square both sides<BR>\n" );
document.write( "n=36.37 which rounds up to 37.  That is unlikely to be changed by using a t-value<BR>\n" );
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