document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1193364>Question 1193364</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Calcium is essential to tree growth. In​ 1990, the concentration of calcium in precipitation in a certain area was 0.15 milligrams per liter. A random sample of 10 precipitation dates in 2018 results in the following data table.\r<BR>\n" );
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document.write( "(a) State the hypotheses for determining if the mean concentration of calcium precipitation has changed since 1990.\r<BR>\n" );
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document.write( "​(b) With 95​% ​confidence, the mean concentration of calcium in precipitation in this area in 2018 is between blank mg/ml and blank mg/ml \r<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 #825423 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=825423\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Need the data table.<BR>\n" );
document.write( "No, you don't have to pay.<BR>\n" );
document.write( "In order to answer the question, we need the variance.<BR>\n" );
document.write( "the 95% half-interval is t(0.975, df=9)*s/sqrt(10)<BR>\n" );
document.write( "I know the past mean, but I do not know the mean of the 10 values. I know t, but I do not know s, the std dev. of the sample. The mean and sd of the sample of 10 are both needed.<BR>\n" );
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