document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=870607>Question 870607</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A new type of light bulb has an average lifespan of 1200 hours with a standard deviation of 75 hours<BR>\n" );
document.write( "Use the table to find out the probability that a lightbulb chosen at random will last 1140-1260 hours </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #524979 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=524979\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Convert the raw score of x = 1140 to a standard z-score\r<BR>\n" );
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document.write( "z = (x-mu)/sigma<BR>\n" );
document.write( "z = (1140-1200)/75<BR>\n" );
document.write( "z = -0.80\r<BR>\n" );
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document.write( "Now use <a  rel=nofollow HREF=\"http://www.math.upenn.edu/~chhays/zscoretable.pdf\">this table</a> to find the area to the left of z = -0.80\r<BR>\n" );
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document.write( "That area is 0.2119. Let's call this area1\r<BR>\n" );
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document.write( "Convert the raw score of x = 1260 to a standard z-score\r<BR>\n" );
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document.write( "z = (x-mu)/sigma<BR>\n" );
document.write( "z = (1260-1200)/75<BR>\n" );
document.write( "z = 0.80\r<BR>\n" );
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document.write( "Now use <a  rel=nofollow HREF=\"http://www.math.upenn.edu/~chhays/zscoretable.pdf\">this table</a> to find the area to the left of z = 0.80\r<BR>\n" );
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document.write( "That area is 0.7881. Let's call this area2\r<BR>\n" );
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document.write( "Now subtract the two areas: \r<BR>\n" );
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document.write( "Area2 - Area1 = 0.7881 - 0.2119 = 0.5762\r<BR>\n" );
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document.write( "The area between z = -0.80 and z = 0.80 is approximately 0.5762\r<BR>\n" );
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document.write( "So the area between x = 1140 and x = 1260 is also approximately 0.5762\r<BR>\n" );
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document.write( "That means the probability is about <font color=\"red\">0.5762</font> (roughly 57.62%)<BR>\n" );
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