Abstract
Sample Entropy is calculated by means of three parameters, i.e. N as the length of the time series, m as the length of sequences to be compared, and r as the tolerance for accepting matches, where r * SD is the standard deviation of the data set. The Sample Entropy (SampEn) value is an indicator that can reveal potential regularity and periodicity of data that otherwise cannot be recognized from a complicated random data set. The conventional method is to compare m and r as empirical value but this time, applying the new method we compared the r-SampEn value for each m =2 to10 with r = 0.1 to 0.5 with increments of 0.01. As a result, surprisingly, we found that the behavior of the SampEn (especially where m = 2, 3, 4) towards the photoplethysmographic value m of people with a mental disorder is slightly different according to the type of disease but similar for patients who are diagnosed with the same mental disease. This is a remarkable phenomenon that needs further research. Hence, we will try to clarify this outcome theoretically and hope to find ways to apply this indicator in order to diagnose and cure patients.