document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1180195>Question 1180195</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Suppose that a brand of lightbulb lasts on average 2243 hours with a standard deviation of 199 hours. Assume the life of the lightbulb is normally distributed. Calculate the probability that a particular bulb will last from 1797 to 2406 hours?\r<BR>\n" );
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document.write( "P(1797 < X < 2406) = \r<BR>\n" );
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document.write( "Enter your answer as a number accurate to 4 decimal places.\r<BR>\n" );
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document.write( "*Note: all z-scores must be rounded to the nearest hundredth. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #809805 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=809805\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> z=(x-mean)/sd<BR>\n" );
document.write( "z lower=(1797-2243)/199=-2.24<BR>\n" );
document.write( "z upper=163/199=0.82<BR>\n" );
document.write( "the probability is 0.7813<BR>\n" );
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document.write( "check on calculator with 2 VARS 2 normalcdf (1797,2406,2243,199)ENTER=0.7811, which is slightly more accurate, since the z-values are not rounded until the calculation. This is obtained with 3 decimal places for z.<BR>\n" );
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