Table 3.

Features considered for training.

Feature name	Symbol per axis	Meaning
Mean	$\overline{x}$, $\overline{y}$, $\overline{z}$	Statistical tendency of a group of samples from the same axis
Standard deviation	std(x), std(y), std(z)	Measure of variability of a group of samples from the same axis
Variance	var(x), var(y), var(z)	Measure of variability of the squares of a group of samples from their corresponding mean
Mean absolute deviation	MAD(x), MAD(y), MAD(z)	Measure of variability of a group of samples from their corresponding mean
Difference of means	$\stackrel{=}{x}-\overline{y}$, $\overline{y}-\overline{z}$, $\overline{x}-\overline{z}$	Difference between means of two different axes