document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1182979>Question 1182979</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 430 babies were born, 344 of them were girls. Use the sample data to construct a 99% confidence interval estimate of the percentage of girls born. Based on result, does the method appear to be effective?\r<BR>\n" );
document.write( "\n" );
document.write( "( ) < p < ( )\r<BR>\n" );
document.write( "\n" );
document.write( "The proportion is different from 0.5? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #813142 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=813142\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> p hat=344/430=0.8<BR>\n" );
document.write( "half-interval is z(0.995)*sqrt(.8*.2/430)<BR>\n" );
document.write( "=2.575*sqrt(.16/430)<BR>\n" );
document.write( "=0.0497<BR>\n" );
document.write( "the interval is 0.75 < p < 0.85<BR>\n" );
document.write( "Since the interval does not contain 0.5, yes, the proportion is different from 0.5<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );