document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=391962>Question 391962</A>: <I><SPAN STYLE=\"word-break: break-all;\"> . A factory produces very small electric light bulbs. It is known from experience that 6% of the bulbs produced are defective, i.e. they do not work.\r<BR>\n" );
document.write( "\n" );
document.write( "Another factory uses these bulbs in strings of lights used to decorate Christmas trees, where each string contains 50 light bulbs.\r<BR>\n" );
document.write( "\n" );
document.write( "For a string of lights, calculate,\r<BR>\n" );
document.write( "\n" );
document.write( "(a)	the mean number of bulbs which are defective\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "(b)	the variance of the number of defective bulbs\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "(c)	the standard deviation of the number of defective bulbs\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "(d)	The company that produces the strings of lights packages each string in a box. The company also wishes to include a small packet of spare bulbs in the box. Using your answers from (a), (b) and (c) above, how many spare bulbs should they include with each string?\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #278150 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=278150\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  A factory produces very small electric light bulbs. It is known from experience that 6% of the bulbs produced are defective, i.e. they do not work. <BR>\n" );
document.write( "Another factory uses these bulbs in strings of lights used to decorate Christmas trees, where each string contains 50 light bulbs. <BR>\n" );
document.write( "For a string of lights, calculate, <BR>\n" );
document.write( "(a) the mean number of bulbs which are defective<BR>\n" );
document.write( "np = 50*0.06 = 3 <BR>\n" );
document.write( "------<BR>\n" );
document.write( "(b) the variance of the number of defective bulbs <BR>\n" );
document.write( "npq = 3*0.4 = 1.2<BR>\n" );
document.write( "------<BR>\n" );
document.write( "(c) the standard deviation of the number of defective bulbs <BR>\n" );
document.write( "sqrt(npq) = sqrt(1.2) = 1.095..<BR>\n" );
document.write( "------<BR>\n" );
document.write( "(d) The company that produces the strings of lights packages each string in a box. The company also wishes to include a small packet of spare bulbs in the box. Using your answers from (a), (b) and (c) above, how many spare bulbs should they include with each string?<BR>\n" );
document.write( "Guess: 53<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. \r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );