document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1177069>Question 1177069</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Insurance companies are becoming concerned that the increased use of cell phones is resulting in more car crashes, and they are considering implementing higher rates for drivers who use such phones. They want to estimate the proportion of drivers who talk on phone while they are driving to within 3% with 95% confidence. What size of 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 #805268 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=805268\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> error is half-interval, which is for a proportion z*sqrt(p*(1-p)/n)<BR>\n" );
document.write( "so 1.96*sqrt(0.03*0.97/n)=0.03<BR>\n" );
document.write( "square both sides<BR>\n" );
document.write( "3.8416*0.0291/n=0.0009<BR>\n" );
document.write( "n=124.21 or 125 </SPAN>\n" );
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