I am studying the potential of DCT and FFT coefficients extracted from a signal to classify the different objects that emit the signal. I applied the Shapiro-Wilk to confirm that data was not normally distributed and proceeded with non-parametric testes (Kruskall-Wallis and Mann-Whitney). However, I see that the range of each variable (coefficient 1, coefficient 2, etc) is very wide, with small values (1) and very large (3000). Besides, I obtain p-value values such e-218, which makes me wonder if this is the correct approach or if any additional procedures must be conducted. This is my first work involving statistical analysis, any suggestion? I can't seem to find much procedures on such type of data in the literature.

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