Table 4.

Statistical indicators and their mathematical expression for designing the fuzzy rules.

Indicator	Mathematical expression
Mean	$\overline{x}=\frac{{\sum }_{i=1}^n{x}_i}{n}$
Standard deviation	$\mathrm{SD}=\sqrt{\frac{{\sum }_{i=1}^n{(x_i-\overline{x})}^2}{n-1}}$
Median	$\mathrm{median}=\left(\frac{n+1}{2}\right)\mathrm{th ordered observation}$
Energy	$\mathrm{E}=\frac{{\sum }_{i=1}^n{\sum }_{j\ne i=1}^n{|x}_i-x_j|}{n^2}$
Coefficient of skewness	$\mathrm{CS}=\frac{n{\sum }_{i=1}^n{(x_i-\overline{x})}^3}{{\left[\mathrm{SD}\right]}^3}$
Coefficient of kurtosis	$\mathrm{CK}=\frac{n{\sum }_{i=1}^n{(x_i-\overline{x})}^4}{{\left[\mathrm{SD}\right]}^4}-3$
Harmonic mean	$\mathrm{HM}=\frac{n}{{\sum }_{i=1}^{n}1/x_i}$
Mean deviation	$\mathrm{MD}=\frac{{\sum }_{i=1}^n{|x}_i-\overline{x}|}{n}$

Where $n$ represents the sample size corresponding to each one-dimensional array data set, and $x_i$ is observation $i$ of each ECG data set (sample), while $\overline{x}$ is the mean value of each data set.