document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=314033>Question 314033</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am working my statistics class, and am having issues finding the correct formula for finding the following:\r<BR>\n" );
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document.write( "The average diameter of certain Euro coins is a number in millimeters with a standard deviation of a number in millimeters.  If 9 coins are chosen at random, find the probability that the average diameter of those coins is more than a number in millimeters.  Assume that the variable is normally distributed.\r<BR>\n" );
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document.write( "I have been using the following formula, but it is not working right, because I'm not sure what to do with the 9 coins:\r<BR>\n" );
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document.write( "z = Value - mean / standard deviation\r<BR>\n" );
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document.write( "I did not want you to work the problem for me, I just need assistance without getting the answer.\r<BR>\n" );
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document.write( "Thank You in advance...Rosanna </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #224502 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=224502\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I am working my statistics class, and am having issues finding the correct formula for finding the following: <BR>\n" );
document.write( "The average diameter of certain Euro coins is a number in millimeters with a standard deviation of a number in millimeters. <BR>\n" );
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document.write( "Let assume average = u and the standard deviation is s.<BR>\n" );
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document.write( "If 9 coins are chosen at random, find the probability that the average diameter of those coins is more than a number (k) in millimeters. <BR>\n" );
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document.write( "Assume that the variable is normally distributed. <BR>\n" );
document.write( "I have been using the following formula, but it is not working right, because I'm not sure what to do with the 9 coins:<BR>\n" );
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document.write( "The Central Limit Theorem guarantees <BR>\n" );
document.write( "1. the mean of ALL the sample means of size 9 is u (the same mean as the population.<BR>\n" );
document.write( "BUT<BR>\n" );
document.write( "2. the std of ALL the samples of size 9 is s/sqrt(n) where n is the sample size.<BR>\n" );
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document.write( "So your formula should be:<BR>\n" );
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document.write( "z = (Value - mean) / [standard deviation/sqrt(9)]<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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