Root Mean Square Deviation
The standard deviation is also called the ROOT MEAN SQUARE DEVIATION. This is because it is the
ROOT (Step 4)
of the MEAN (Step 3)
of the SQUARES (Step 2)
of the DEVIATIONS (Step 1) of the observations from their mean.
The standard deviation is a measure of dispersion.
It is expressed in the same units as the data.
It is superior to other measures of dispersion because the positive and negative deviations do not cancel out.
It does not involve quantities like |X – Mean| which have two meanings.
It is also known as the root mean square deviation.