document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1043430>Question 1043430</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In a survey of 3095 &#8203;adults, 1415 say they have started paying bills online in the last year.<BR>\n" );
document.write( "Construct a&#8203; 99% confidence interval for the population proportion. Interpret the results. Round to three decimal places as needed  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #658576 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=658576\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 99% CI is z*sqrt{ p*(1-p)/n}<BR>\n" );
document.write( "z=2.576<BR>\n" );
document.write( "p=1415/3095=0.4572<BR>\n" );
document.write( "1-p=0.5428<BR>\n" );
document.write( "sqrt of {0.4572*0.5428/3095}=0.00895<BR>\n" );
document.write( "multiply that by 2.576 to get the interval width on each side of the point estimate, which is 0.4572.<BR>\n" );
document.write( "0.023067<BR>\n" );
document.write( "(0.434,0.480)<BR>\n" );
document.write( "We don't know the true proportion who stated they have started paying bills online in the last year, but we are extremely confident, 99% so, that the true number lies in the above interval.<BR>\n" );
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