Variance (with 2 ): This is the most famous measure for assessing variability because it represents is the squared deviation. This can be called the root mean square error, because it is the mean of the standard deviation.
Average absolute deviation: you can estimate the typical estimate of these deviations. If we average the values, negative deviations will displace positive ones. Also, the sum of deviations from the mean is always zero. Thus, this is a simple approach for averaging the deviation itself.
Sequence: [2, 4, 6, 8] Mean = 5 Deviation around mean = [-3, -1, 1, 3] Mean Absolute Deviation = (3 + 1 + 1 + 3) / 4