document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1048818>Question 1048818</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I really need some assistance on this problem:\r<BR>\n" );
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document.write( "You take a sample of 22 from a population of test scores and the mean of your sample is 60. \r<BR>\n" );
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document.write( "(a) You know the standard deviation of the population is 10. What is the 99% confidence interval on the population mean. \r<BR>\n" );
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document.write( "(b) Now assume that you do not know the population standard deviation, but the standard deviation in your sample is 10. What is the 99% confidence interval on the mean now?\r<BR>\n" );
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document.write( "Any help is greatly appreciated! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #664414 by </B><A HREF=/tutors/aboutme.mpl?userid=ewatrrr><B>ewatrrr(24785)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ewatrrr><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=ewatrrr><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=664414\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a)<BR>\n" );
document.write( "For a population with unknown mean  and known standard deviation , <BR>\n" );
document.write( "a confidence interval for the population mean is: CI = x-bar ± <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=z%2Asigma%2Fsqrt%28n%29 ALIGN=MIDDLE  ALT=\"z%2Asigma%2Fsqrt%28n%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "CI =  = 60 ± <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=z%2A10%2Fsqrt%2822%29 ALIGN=MIDDLE  ALT=\"z%2A10%2Fsqrt%2822%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > 99% confidence level: z = 2.576<BR>\n" );
document.write( "CI =  = 60 ± <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2.576%2A10%2Fsqrt%2822%29 ALIGN=MIDDLE  ALT=\"2.576%2A10%2Fsqrt%2822%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "b)<BR>\n" );
document.write( "For a population with unknown mean  and unknown standard deviation , <BR>\n" );
document.write( "a confidence interval for the population mean is: CI = x-bar ± <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%2As%2Fsqrt%28n%29 ALIGN=MIDDLE  ALT=\"t%2As%2Fsqrt%28n%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "CI = 60 ± <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%2A10%2Fsqrt%2822%29 ALIGN=MIDDLE  ALT=\"t%2A10%2Fsqrt%2822%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > <BR>\n" );
document.write( "99% confidence level, Degree of Freedom(n-1) = 21: t = 2.83 (use Caculator 0r table)<BR>\n" );
document.write( "CI = 60 ± <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2.831%2A10%2Fsqrt%2822%29 ALIGN=MIDDLE  ALT=\"2.831%2A10%2Fsqrt%2822%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >  </SPAN>\n" );
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