An example is shown in the left panel of Fig. 4, where the data are significantly more scattered than the data in the left panel of Fig.3, which correspond to the mean values. The deviations relative to the expected steady conditions are indicated by the fact that many data points fall outside the limiting curves corresponding to the values of the mean power curves above which 5% and 95% of the observations fall (so-called percentiles).Therefore, we have considered for analysis only the vibration measurements associated with output power levels lying between the estimated percentiles in the range from 4 to 12 m/s. Then, for the vibration measurements above 12 m/s, only those data corresponding to output power values between 1900 and 2100kW have been preserved. As an example, the final set of selected data points considered for the study of turbine T2 is shown in the right panel of Fig. 4.