document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1185622>Question 1185622</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Zodwa,the operations manager of a large production plant would like to estimate the mean amount of time a worker takes to assemble a new electronic component. Assume that the standard deviation of this assembly time 3.6 minutes.<BR>\n" );
document.write( "(a) After observing 120 workers assembling similar devices, Zodwa noticed that their average time was 16.2 minutes. Construct a 92% confidence interval for the mean assembly time.\r<BR>\n" );
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document.write( "(b) How many workers should be involved in this study in order to have the mean assembly time estimated up to plus or minus 15 seconds with 92% confidence? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #816459 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=816459\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 92% half-interval is z(0.96)*3.6/sqrt(120)=1.75*3.6/sqrt(120)=0.575<BR>\n" );
document.write( "the interval is (15.625 min, 16.775 min)<BR>\n" );
document.write( "-<BR>\n" );
document.write( "error is the half-interval<BR>\n" );
document.write( "so e=z(0.96)(sigma/sqrt(n)), error is 0.25 min<BR>\n" );
document.write( "0.25=1.75*3.6/sqrt(n)<BR>\n" );
document.write( "square both sides and move n over<BR>\n" );
document.write( "0.0625n=39.69<BR>\n" );
document.write( "n=635.04 or 636 people<BR>\n" );
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