document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=225375>Question 225375</A>: <I><SPAN STYLE=\"word-break: break-all;\"> THis question is coming from Quantitive Methods and concerns Marginal and Joint probability. It is a 2 part question. I completely do not understand how to solve this problem. I do not understand how to formulate to solve:\r<BR>\n" );
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document.write( "\"A metro school system consists of 2 districts: north and south. The north district contains 60% of all students and the south district contains 40% of all students. A competency test was given to all students. 10% of the north district failed and 15% of the south district failed.\"\r<BR>\n" );
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document.write( "Question A: What is the probability that a student from the entire school system, chosen at random, has passed?\r<BR>\n" );
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document.write( "Question B using Bayes Rule: What is the probability that a student who has failed the test came from the South District?\r<BR>\n" );
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document.write( "Any help is learning how to EASILY formulate and solve would be appreciated. Thanks! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #168183 by </B><A HREF=/tutors/aboutme.mpl?userid=scott8148><B>scott8148(6628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=scott8148><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=scott8148><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=168183\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> working with a numerical example makes this more straight forward\r<BR>\n" );
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document.write( "say 1000 students in the system\r<BR>\n" );
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document.write( "\"The north district contains 60% of all students\" ___ (60%)1000 = 600\r<BR>\n" );
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document.write( "\"the south district contains 40% of all students\" ___ (40%)1000 = 400\r<BR>\n" );
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document.write( "\"10% of the north district failed\" ___ (10%)600 = 60\r<BR>\n" );
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document.write( "\"15% of the south district failed\" ___ (15%)400 = 60\r<BR>\n" );
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document.write( "A: 120 out of 1000 failed, so 880 passed (1000-120)<BR>\n" );
document.write( "___ probability of a student from the system passing is 880/1000 or .88\r<BR>\n" );
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document.write( "B: 120 failed and 60 of those came from South<BR>\n" );
document.write( "___ probability of a failed student from South is 60/120 or .5 </SPAN>\n" );
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