document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1142943>Question 1142943</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In order to find a t-value separating the confidence interval we need to know:\r<BR>\n" );
document.write( "\n" );
document.write( "Sample size and confidence level\r<BR>\n" );
document.write( "\n" );
document.write( "Confidence Level and sample mean\r<BR>\n" );
document.write( "\n" );
document.write( "Sample mean and sample standard deviation\r<BR>\n" );
document.write( "\n" );
document.write( "Confidence Level and z-score </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #763892 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=763892\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> i think you will need the sample size and the confidence level.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the confidence level tells you how wide the confidence interval is.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "for example, if the confidence level is .9, then you will need to find the t-score corresponding to an area to the left of it of .05 and the t-score corresponding to an area to the left of it of .95.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "once you find that, you can find the area between those t-scores.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "in order to find the t-score, however, you will also need to find the sample size.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "from the sample size, you can get the degrees of freedom.<BR>\n" );
document.write( "the degrees of freedom is equal to the sample size minus 1.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "for example:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "assume the confidence level is 90% = .9<BR>\n" );
document.write( "that give you an alpha of 1 - .9 = .1.<BR>\n" );
document.write( "this alpha is split between the left hand side of the confidence interval and the right hand side of the confidence interval.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "assume the sample size is 30.<BR>\n" );
document.write( "the degrees of freedom become 29.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "you look in the t-score table for a two tail alpha of .10, which corresponds to a one tail alpha of .05.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "you then look down the table for 29 degrees of freedom and the table tells you that the t-score corresponding to that would be equal to plus or minue 1.699.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "you can also use a t-score calculator to get the same thing.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the table i used can be found at <a  rel=nofollow HREF= \"http://www.ttable.org/\" target = \"_blank\">http://www.ttable.org/</a>\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the t-score calculator i used can be found at <a  rel=nofollow HREF= \"https://goodcalculators.com/student-t-value-calculator/\" target = \"_blank\">https://goodcalculators.com/student-t-value-calculator/</a>\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the t-score graph generator i used can be found at <a  rel=nofollow HREF= \"https://mathcracker.com/t-distribution-graph-generator.php#results\" target = \"_blank\">https://mathcracker.com/t-distribution-graph-generator.php#results</a>\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "i also used the TI-84 Plus calculator which told me that the critical t-scores needed to be plus or minus 1.699126996.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "those t-scores more detailed than the rounded results from the table and frm the online calculator.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );