7
8
9
10
11
12
13
-3
-2
-1
0
1
2
3
4
--------------
28
S.D = ∑(x−x)2N=∑d2N=287\frac{\sqrt{\sum (x - x)^2}}{N} = \frac{\sum d^2}{N} = \frac{\sqrt{28}}{7}N∑(x−x)2=N∑d2=728
= 4\sqrt{4}4
= 2
