March 29, 2018
Standard Deviation. The standard deviation of a set of numbers, xn, n = 1, …, N, is given by
The standard deviation is a measure of the variability of a signal about its mean value. For a vibration signal with a mean value of zero, the standard deviation is equal to the RMS (root-mean-square) value of the signal. Referring back to the vibration signal used in Figs. 1 & 2, the standard deviation and RMS level have a value of 0.073 G.
The variance and standard deviation play an important role in determining the confidence interval (or conversely the uncertainty) of a statistical measure. This is discussed further in the lesson on Confidence Intervals.