a user - friendly and statistic based heart rate variability analytical method includes the following steps of capturing an electrocardiogram signal of a person , performing analog - to - digital conversion of the electrocardiogram signal , selecting the peaks of the electrocardiogram signal , calculating the standard deviation of the heights , durations and inter - peak intervals of the peaks , removing the peaks whose heights , durations or inter - peak duration fall beyond a first predetermined standard deviation , sampling and interpolating the qualified peaks to form a consecutive peak signal , and performing spectrum analysis to the peak signal in frequency domain .