Here xi = 6, 7, 10, 12, 13, 4, 8, 12
∴ Σ xi = 6 + 7 + 10 + 12 + 13 + 4 + 8 + 12 = 72; n = 8
∴ Mean (

−

x

) =

72

8

= 9
Now, Sx2i= (6)2+(7)2+(10)2+(12)2 + (13)2+(4)2+(8)2+(12)2
= 36 + 49 + 100 + 144 + 169 + 16 + 64 + 144 = 722
∴ Variance (σ2) =

nΣxi2−(Σxi)2

n2

=

8×722−(72)2

(8)2

=

5776−5184

64

=

592

64

= 9.25