document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1138417>Question 1138417</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi! I'm stumped on the second part of this question. Could someone explain the steps for me please?\r<BR>\n" );
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document.write( "The mean travel time to work in the US is 25.1 minutes with a standard deviation of 6.4 minutes.\r<BR>\n" );
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document.write( "a. Find the probability that a random sample of 36 people will have a mean travel time greater than 23 minutes. (I got 0.9755)\r<BR>\n" );
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document.write( "b. Find the 90th percentile of the sample mean for those 36 people. (The answer key says it's 26.467, but I cannot figure out the steps!)\r<BR>\n" );
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document.write( "Thanks in advance. :) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #756223 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=756223\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> z>(x bar-mean)/sigma/sqrt (n)<BR>\n" );
document.write( "z>(23-25.1)*6/6.4<BR>\n" );
document.write( "z>-1.96875<BR>\n" );
document.write( "0.9755 is correct\r<BR>\n" );
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document.write( "z for the 90th percentile is 1.28<BR>\n" );
document.write( "1.28=(x bar-mean)/sigma/sqrt (n) or (x bar-mean) divided by 6.4/6, which is 1.067<BR>\n" );
document.write( "8.19=6(x bar-mean)<BR>\n" );
document.write( "1.367=x bar-mean<BR>\n" );
document.write( "x bar=26.467 min </SPAN>\n" );
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