Editing Variance (section)

===Units of measurement===

Unlike the [[Average absolute deviation|expected absolute deviation]], the variance of a variable has units that are the square of the units of the variable itself.  For example, a variable measured in meters will have a variance measured in meters squared.  For this reason, describing data sets via their [[standard deviation]] or [[root mean square deviation]] is often preferred over using the variance.  In the dice example the standard deviation is {{math|{{sqrt|2.9}} ≈ 1.7}}, slightly larger than the expected absolute deviation of&nbsp;1.5.

The standard deviation and the expected absolute deviation can both be used as an indicator of the "spread" of a distribution.  The standard deviation is more amenable to algebraic manipulation than the expected absolute deviation, and, together with variance and its generalization [[covariance]], is used frequently in theoretical statistics; however the expected absolute deviation tends to be more [[Robust statistics|robust]] as it is less sensitive to [[outlier]]s arising from [[measurement error|measurement anomalies]] or an unduly [[heavy-tailed distribution]].