document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=280196>Question 280196</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A certain type of thermal bettery for an airplane navigation device backup power has a mean life of 300 hours with a standard deviation of 15 hours. What proportion of these batteries can be expected to have lives of 322 hours or less? Assume a normal distribution of backup power devices lives.\r<BR>\n" );
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document.write( "I'm so confused about what I am supposed to do. Here is what I have tried:\r<BR>\n" );
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document.write( "15+300/322= 5130/322=15.9<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 #203662 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=203662\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A certain type of thermal bettery for an airplane navigation device backup power has a mean life of 300 hours with a standard deviation of 15 hours. What proportion of these batteries can be expected to have lives of 322 hours or less? Assume a normal distribution of backup power devices lives. <BR>\n" );
document.write( "I'm so confused about what I am supposed to do. Here is what I have tried: <BR>\n" );
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document.write( "To get unconfused:<BR>\n" );
document.write( "Sketch a normal curve.<BR>\n" );
document.write( "Put 300 at the middle of the x-axis under the curve.<BR>\n" );
document.write( "Put 15 under the 300 just to remind yourself that 15 is the std.<BR>\n" );
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document.write( "Mark 322 at an apporiate point on the x-axis.<BR>\n" );
document.write( "Shade the area under the curve and to the left of 322.<BR>\n" );
document.write( "That shaded area is the answer to your problem.<BR>\n" );
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document.write( "Find the z-value of 322:<BR>\n" );
document.write( "z(322)= (322-300)/15 = 1.467<BR>\n" );
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document.write( "The following you just have to understand.<BR>\n" );
document.write( "Use your z-chart or your calculator to get:<BR>\n" );
document.write( "P(x < 322) = P(z < 1.467) = 0.9288<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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