2 2
n- x
n
x ⎟
⎠
⎜ ⎞
⎝
σ= ∑ ⎛∑2
8- 120
8
(^1940) ⎟
⎠
⎜ ⎞
⎝
= ⎛
= 242. 5 − 225
= 17. 5
σ = 4.18- Variance
Variance is the square of the standard deviation.
Variance, nd^ nd(^22) ∑ 2
⎟⎟ =
⎠
⎞
⎜⎜⎝
σ=⎛ ∑
Once the child is through with the idea of standard deviation, the concept of variance
can be introduced stating clearly the relation between the two.
Eg. : Variance = (Standard deviation)^2
Hence in the previous example, Variance = 17.5