Question 1113619
.
<pre>
If in your notation xbar means the MEAN value of the series, then this sum  &#931;(x – xbar)  is zero.



This sum is ALWAYS zero for ANY finite series.



Particularly, it is equal to zero for the given particular series.


     Original          Centered
      values        values x-xbar
------------------------------------

	7	       -0.2
	6	       -1.2
	10      	2.8
	7	       -0.2
	5	       -2.2
	9	        1.8
	3	       -4.2
	7	       -0.2
	5	       -2.2
	13	        5.8
sum =	72	
xbar = 	7.2      sum =	0
</pre>