document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1064881>Question 1064881</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Use the normal distribution to approximate the desired probability. A coin is tossed 20 times. A person, who claims to have extrasensory perception, is asked to predict the outcome of each flip in advance. She predicts correctly on 13 tosses. What is the probability of being correct 13 or more times by guessing? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #680102 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=680102\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> np=10 mean<BR>\n" );
document.write( "np(1-p)=variance=5<BR>\n" );
document.write( "sd=sqrt (5) or 2.236<BR>\n" );
document.write( "probability of 13 or more is (13-10)/2.236=probability z >1.342, which is 0.0898\r<BR>\n" );
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document.write( "The probability is 20C13 (0.5^13)(0.5^7)=0.0739, which is the exact probability. </SPAN>\n" );
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