“…Within such a long history and wide research scope, different domain groups of methods were evaluated: - time domain indexes based on step response: undershoot, overshoot, response times, area index, output index, R-index, idle index, etc. ;
- time-series-based indexes: mean square error (MSE), integral of absolute error (IAE), amplitude index (AMP);
- statistical factors utilizing different probabilistic distribution function (standard deviation, variance, skewness, kurtosis, scale or shape, ...);
- minimum variance and model-based measures;
- novel indexes using wavelets, Fourier transform, orthonormal functions, singular spectrum analysis, neural networks, Hurst exponent, persistence measures, entropy, ...; and
- business KPIs expressed in monetary terms.
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