document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=715927>Question 715927</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The help desk for a software company logs the lengths of times of each call that technicians have with customers. Historical records based on the past 3 years indicate that call length (L) is a normally distributed variable with an average (&#956;) of 9.00 minutes and a standard deviation (&#963;) of 0.95 min. For each of the problems below, find the appropriate probability. <BR>\n" );
document.write( "A) P(L &#8804; 10.22)    \r<BR>\n" );
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document.write( "B) P(L > 10.74)    \r<BR>\n" );
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document.write( "C) P(7.67 &#8804; L < 11.02)    \r<BR>\n" );
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document.write( "D) The call times that enclose the central 81% of the distribution are: <BR>\n" );
document.write( "    Note: Round your answers to two decimal places for this problem.\r<BR>\n" );
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document.write( "I really need step by step help. Im not coming up with the correct answers..<BR>\n" );
document.write( "    Low:            to High:   </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #439751 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=439751\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> call length (L) is a normally distributed variable with an average (&#956;) of 9.00 minutes and a standard deviation (&#963;) of 0.95 min. For each of the problems below, find the appropriate probability. <BR>\n" );
document.write( "A) P(L &#8804; 10.22)<BR>\n" );
document.write( "z(10.22) = (10.22-9)/0.95 = 1.2842<BR>\n" );
document.write( "Ans: P(L<= 10.22) = P(z<=1.2842) = normalcdf(-100,1.2842) = 0.9005<BR>\n" );
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document.write( "B) P(L > 10.74)<BR>\n" );
document.write( "Find the z-value of 10.74.<BR>\n" );
document.write( "Find the P(z is above that z-value)<BR>\n" );
document.write( "Ans: 0.0335<BR>\n" );
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document.write( "C) P(7.67 &#8804; L < 11.02)<BR>\n" );
document.write( "Find the z-value of those numbers.<BR>\n" );
document.write( "Find the P(z is between those z-values)<BR>\n" );
document.write( "Ans: 0.9025<BR>\n" );
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document.write( "D) The call times that enclose the central 81% of the distribution are: <BR>\n" );
document.write( "Note: Round your answers to two decimal places for this problem.<BR>\n" );
document.write( "Draw the picture:<BR>\n" );
document.write( "You have a left tail of 0.5000- 0.4150 = 0.085<BR>\n" );
document.write( "invNorm(0.085) = -1.3722 for the left tail and +1.3722 for the right tail:<BR>\n" );
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document.write( "Find the corresponding x-value using x = z*s+u<BR>\n" );
document.write( "x = -1.3722*0.95+9 = 7.70<BR>\n" );
document.write( "x = +1.3622*0.95+9 = 10.30<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H. <BR>\n" );
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