> verba docent exempla trahunt ~Seneka

Take three numbers: 1, 2 and 3.

Mean value is 2

Differences between values and a mean are:

1-2 = -1

2-2 = 0

3-2 = 1

Sum of these differences is

-1 + 0 + 1 = 0

Zero-sum property states that no matter what numbers you start with, a result (sum of diiferences between them and their mean) would be 0