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December 3rd, 2016, 12:52 AM  #1 
Senior Member Joined: Aug 2014 From: Mars Posts: 101 Thanks: 9  Comparisons
Class has gotten to me. I can't get a hold of my teacher over the weekend so I'm hoping you guys can understand my question. There is this equation: $\displaystyle \sum c^2 = \left ( 1 \right )^{2} + \left ( 1 \right )^{2}$ that I don't understand why the second one is negative. Each number is supposed to represent a group. So if I were to compare one group to two groups I would should do this equation: $\displaystyle \sum c^2 = \left ( 1 \right )^{2} + \left (\frac{1}{2} \right )^{2} + \left (\frac{1}{2} \right )^{2}$ Why is the negative number there? I get the feeling that the question is out of context, let me know what you need from me to clarify. 
December 3rd, 2016, 10:21 AM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 1,857 Thanks: 961 
if I saw $\sum c^2 = (1)^2 + (1)^2$ my immediate interpretation would be that $c \in \{1,~1\}$ without further context I don't know what we can tell you. 
December 4th, 2016, 12:59 AM  #3 
Senior Member Joined: Aug 2014 From: Mars Posts: 101 Thanks: 9 
It's for psychology. The first equation is based on two groups of people only. The second equation is one group being compared to two groups.


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