Mean=(7+8+9+7+8+7+x+8)/8
64=54+x
x=10
Now variance is the average of squares of the difference between original value and data
Therefore Variance=(1^2+0^2+1^2+1^2+0^2+1^2+2^2+0^2)/8 where ^denotes square.
variance=(1+0+1+1+0+1+4+0)/8
Variance=1
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