The root-mean-square (RMS) of a variate , sometimes called the Quadratic Mean, is the Square Root of
the mean squared value of :
Physical scientists often use the term root-mean-square as a synonym for Standard Deviation when they refer to the Square Root of the mean squared deviation of a signal from a given baseline or fit.
See also Arithmetic-Geometric Mean, Arithmetic-Harmonic Mean, Generalized Mean, Geometric Mean, Harmonic Mean, Harmonic-Geometric Mean, Mean, Median (Statistics), Standard Deviation, Variance
Hoehn, L. and Niven, I. ``Averages on the Move.'' Math. Mag. 58, 151-156, 1985.