document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=868533>Question 868533</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 480 babies were born, and 264 of them were girls. Use the sample data to construct a 99% confidence interval estimate of the percentage of girls born. Based on the result, does the method appear to be effective?\r<BR>\n" );
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document.write( "__ <p< __   (Round to three decimal places as needed.)\r<BR>\n" );
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document.write( "(Please show all work, thank you.)<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #523618 by </B><A HREF=/tutors/aboutme.mpl?userid=ewatrrr><B>ewatrrr(24785)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ewatrrr><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=ewatrrr><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=523618\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Ho: u = .50 (probability of having a girl w/o treatment)<BR>\n" );
document.write( "Ha: u  > .50 for clinical trial<BR>\n" );
document.write( "mean = .55<BR>\n" );
document.write( "SD = sqrt(.55*.45) = .4975<BR>\n" );
document.write( "t = (.55-.50)/(.4975/sqrt(480) = .05/.0227 = 2.202 <BR>\n" );
document.write( "P(t > 2.202) = .0141<BR>\n" );
document.write( "At the 99% confidence interval, .0141 > .01<BR>\n" );
document.write( "there is not enough evidence to indicate method is working </SPAN>\n" );
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