document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=261826>Question 261826</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I understand basic probability but am very confused when it comes to the below question.  I don't even have a clue where to start to solve this question.\r<BR>\n" );
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document.write( "	A multiple choice test has 20 questions with each having 4 possible answers with one correct. Assume a student randomly guesses the  answer to every question. \r<BR>\n" );
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document.write( "a. What is the probability of getting exactly 11 correct answers?\r<BR>\n" );
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document.write( "20x4=80 1 right answer from 1 question=1/4\r<BR>\n" );
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document.write( "b. What is the probability of getting less than 9 correct answers? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #192915 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=192915\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A multiple choice test has 20 questions with each having 4 possible answers with one correct. Assume a student randomly guesses the answer to every question.<BR>\n" );
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document.write( "This is a binomial problem because the probability of guessing the right<BR>\n" );
document.write( "answer on each problem is 1/4 and there are n= 20 such problems.<BR>\n" );
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document.write( "a. What is the probability of getting exactly 11 correct answers?<BR>\n" );
document.write( "P(x+11) = 20C11(1/4)^11(3/4)9 = binompdf(20,1/4,11) = 0.0030<BR>\n" );
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document.write( "b. What is the probability of getting less than 9 correct answers?<BR>\n" );
document.write( "P(0<= x <=8) = binomcdf(20,1/4,8) = 0.95907...<BR>\n" );
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document.write( "I used a TI calculator to get these answers.<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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