“…8, although other domains such as frequency and time-frequency have also been explored. Statistical approaches such as Gaussian [53], Skewness [4], Kurtosis [4], median [4,38], root mean square (RMS) [31,39,61], moving average/average [4,5,12,38,51,59,62], moving variance/variance [4,5] and standard deviation [5,10,28,40,51,54] were used in the time domain to smooth the signals and extract features in the vibration data. Among the papers that used signal preprocessing, about 60% of them used statistical techniques.…”