Variability (as name inspires) show how much values/elements are different/diverse from each others. When all values are very close to the mean value, it means we have little variability or diversity.

The common used variability measure is the

*variance*(or*standard deviation*, which is the positive square root of variance). Besides, the*range*measure can indicate the amount of variability within a group of data.
I guess the formula to compute variability is known, but let's show it again:

Suppose we had the following measurements data {5.2, 5.3, 4.95, 5.17, 5.22}.

The diversity/variability within values seems small by inspection. Calculating the variance s^2=0.01717 which is clearly a small value.

But let's see this group of data {30, 45, 39, 28, 42}.

The diversity/variability within values seems large by inspection. Calculating the variance s^2=55.7 which is clearly a large value.

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