document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=865293>Question 865293</A>: <I><SPAN STYLE=\"word-break: break-all;\"> (I'm stuck on this question, can someone please help?)<BR>\n" );
document.write( "Recently, a university surveyed recent graduates of the English Department for their starting salaries. Four hundred graduates returned the survey. The average salary was $25,577. The population standard deviation is $2,566. What is the 95% confidence interval for the mean salary of all graduates from the English Department?\r<BR>\n" );
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document.write( "	 [$25,326, $25,828]<BR>\n" );
document.write( "	 [$25,365, $25,789]<BR>\n" );
document.write( "	 [$25,246, $25,908]<BR>\n" );
document.write( "	 [$25,336, $27,101]<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 #521669 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=521669\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Use <a  rel=nofollow HREF=\"http://3.bp.blogspot.com/_5u1UHojRiJk/TEdJJc6of2I/AAAAAAAAAIE/Ai0MW5VgIhg/s1600/t-table.jpg\">this table</a> to get the critical value of <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=z+=+1.960 ALIGN=MIDDLE  ALT=\"z+=+1.960\"   DISABLED_style= \"max-width:90%; height:auto;\" > (look in the row that starts with <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=infinity ALIGN=MIDDLE  ALT=\"infinity\"   DISABLED_style= \"max-width:90%; height:auto;\" >. In this row, you'll find a value that's above the 95% confidence level, which is 1.960)\r<BR>\n" );
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document.write( "The sample mean is xbar = 25577 (given)<BR>\n" );
document.write( "The population standard deviation is sigma = 2566 (given)<BR>\n" );
document.write( "The sample size is n = 400 (given)<BR>\n" );
document.write( "From above, the critical value for a 95% confidence interval is z = 1.960 (this is approximate)\r<BR>\n" );
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document.write( "We will use these values to plug them into the lower bound L and upper bound U formulas below\r<BR>\n" );
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document.write( "L = xbar - z*sigma/sqrt(n)<BR>\n" );
document.write( "U = xbar + z*sigma/sqrt(n)\r<BR>\n" );
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document.write( "where the confidence interval is [L, U]\r<BR>\n" );
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document.write( "Now let's find the lower bound L of the confidence interval\r<BR>\n" );
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document.write( "L = xbar - z*sigma/sqrt(n)\r<BR>\n" );
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document.write( "L = 25577 - 1.960*2566/sqrt(400)\r<BR>\n" );
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document.write( "L = 25577 - 251.468\r<BR>\n" );
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document.write( "L = 25325.532\r<BR>\n" );
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document.write( "L = 25326\r<BR>\n" );
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document.write( "Now let's find the upper bound U of the confidence interval\r<BR>\n" );
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document.write( "U = xbar + z*sigma/sqrt(n)\r<BR>\n" );
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document.write( "U = 25577 + 1.960*2566/sqrt(400)\r<BR>\n" );
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document.write( "U = 25577 + 251.468\r<BR>\n" );
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document.write( "U = 25828.468\r<BR>\n" );
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document.write( "U = 25828\r<BR>\n" );
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document.write( "So the confidence interval [L,U] is [25326, 25828]\r<BR>\n" );
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document.write( "This is <font color=\"red\">choice A)  [$25,326, $25,828]</font><BR>\n" );
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