The Standard Deviation is
a measure of the dispersion of a data set.
In general statistics it is usually calculated
using the Root
Mean Square Error (RMSE) method:
In Statistical
Process Control and Measurement
Systems Analysis it is often
estimated using the Range
Method.
The standard deviation is
the square root of the variance.
The standard deviation is often preferred
because it has the same units as the characteristic
being measured and so is proportionate to
the characteristic.
