document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=865351>Question 865351</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. Use the table to find the probability that a light bulb chosen at random will last less than 1170 hours.\r<BR>\n" );
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document.write( "How do I find probability using a table? What is the formula?<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 #521656 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=521656\">put this solution on YOUR website!</A><BR><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 the probability that a light bulb chosen at random will last less than 1170 hours. <BR>\n" );
document.write( "How do I find probability using a table? What is the formula?<BR>\n" );
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document.write( "Find the z-value of 1170<BR>\n" );
document.write( "z(1170) = (1170-1200)/75 = -0.4<BR>\n" );
document.write( "Note: That means 1170 is 0.4 standard deviations below the mean.<BR>\n" );
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document.write( "Your Problem:<BR>\n" );
document.write( "P(x < 1170) = P(z < -0.4) = ?<BR>\n" );
document.write( "Note: At this point you have to use your z-chart to find the <BR>\n" );
document.write( "area under the normal curve to the left of z = -0.4.  That<BR>\n" );
document.write( "is the same as the area to the right of +0.4.<BR>\n" );
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document.write( "I use a TI-84 calculator to get normalcdf(-100,-0.4) = 0.3446<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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