document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=722361>Question 722361</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Swift Auto Service has taken advantage of some of the results<BR>\n" );
document.write( "   you provided (HW #4) and has improved their process. Their oil & <BR>\n" );
document.write( "   lube “service time per car” still follows a normal distribution, but<BR>\n" );
document.write( "   now with a mean of 30 minutes per car, and a standard deviation<BR>\n" );
document.write( "   of 4.0 minutes.\r<BR>\n" );
document.write( "\n" );
document.write( "   b) if you select a random sample of 16 oil & lube jobs, what is <BR>\n" );
document.write( "      the probability the sample mean “service time” from that group <BR>\n" );
document.write( "      will be shorter than 28 minutes ?<BR>\n" );
document.write( " <BR>\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 #442806 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=442806\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> follows a normal distribution, but<BR>\n" );
document.write( "now with a mean of 30 minutes per car, and a standard deviation<BR>\n" );
document.write( "of 4.0 minutes. <BR>\n" );
document.write( "b) if you select a random sample of 16 oil & lube jobs, what is <BR>\n" );
document.write( "the probability the sample mean “service time” from that group <BR>\n" );
document.write( "will be shorter than 28 minutes ?<BR>\n" );
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document.write( "x-bar = 28 min<BR>\n" );
document.write( "--------------------<BR>\n" );
document.write( "z(28) = (28-30)/[4/sqrt(16)) = -2<BR>\n" );
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document.write( "P(x-bar < 28) = P(z < -2) = 0.0228<BR>\n" );
document.write( "==============<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "============== </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );