March 29, 2018
Single-number statistical measures that describe random variables are called point estimates. This discussion is limited to random variables that are stationary in time; that is, the point estimates are stable when averaging over a long enough time.
Mean Value Equation
The mean value of a set of numbers, xn, n = 1, …, N, is given by the following equation:
For many vibration signals, such as the one in Figure 3.1, the mean value is near zero. This is because the vibration occurs equally in positive and negative directions about a fixed position.
Note that the electronics of a vibration transducer usually filter out the DC component of a vibration, which is the electrical equivalent of the mean value.