document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1174178>Question 1174178</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 1. A manufacturer of light bulbs produces bulbs that last a mean of 1050 hours with a standard deviation of 100 hours. What is the probability that the mean lifetime of a random sample of 10 of these bulbs is greater than 975 hours?\r<BR>\n" );
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document.write( "2. The average public high school has 535 students with a standard deviation of 98.<BR>\n" );
document.write( "a.	If a public school is selected, what is the probability that the number of students enrolled is less than 550?\r<BR>\n" );
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document.write( "b.	If a random sample of 25 public high schools is selected, what is the probability that the number of the students enrolled is greater than 600?<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 #799706 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=799706\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> z=(x-mean)/sd/sqrt(n)<BR>\n" );
document.write( "> = (975-1050/100/sqrt(10) or -75*sqrt(10)/100 or z>= -2.37<BR>\n" );
document.write( "probability is 0.9911<BR>\n" );
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document.write( "z < (550-535)/98 or < 15/98=0.15<BR>\n" );
document.write( "that probability is 0.5596<BR>\n" );
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document.write( "I assume the question means what is the probability that the mean enrollment of these 25 schools is > 600. <BR>\n" );
document.write( "This is z > (600-535)/98/sqrt(25) or z > 65/19.6 or > 3.32<BR>\n" );
document.write( "that probability is 0.00045 or 0.0005.<BR>\n" );
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