document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1075191>Question 1075191</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please I'm asking for your help to solve the problem.\r<BR>\n" );
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document.write( "The records of a department store show that 10% of their customers who make a purchase return the merchandise in order to exchange it. What is the probability that in the next eight purchases at least three customers return the merchandise for exchange?<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #690034 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=690034\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Use the binomial probability distribution<BR>\n" );
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document.write( "Probability(P) (k successes out of n trials) = nCk * p^k * (1-p)^(n-k), where n is the number of trials, k is the number of successes, p is probability of success, nCk is combination of n trials taken k at a time( n! / k! * (n-k)!)<BR>\n" );
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document.write( "P(in 8 purchases at least 3 customers return purchases) = 1 -P(0 purchase returned) -P(1 purchase returned) - P(2 purchases returned)<BR>\n" );
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document.write( "Note that n = 8, p = 0.10, k is 0, 1, 2<BR>\n" );
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document.write( "P(in 8 purchases at least 3 customers return purchases) = 1 -0.43 -0.38 -0.15 = 0.04<BR>\n" );
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document.write( "Note this solution assumes that each customer makes 1 purchase<BR>\n" );
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