Table 7. Correlation and effect size metrics measuring the agreement between the SDNN, lnSDNN, RMSSD, and pNN50 values derived from rPPG recordings of different lengths and the metrics derived from the 60 s reference (PPG) recordings.
| 10s-1 | 10s-2 | 10s-3 | avg10s | 30s-1 | 30s-2 | avg30s | |
|---|---|---|---|---|---|---|---|
| Spearman coefficient* | |||||||
| SDNN | 0.555 (p < 0.001) |
0.543 (p < 0.001) |
0.599 (p < 0.001) |
0.727 (p < 0.001) |
0.733 (p < 0.001) |
0.695 (p = 0.001) |
0.800 (p < 0.001) |
| RMSSD | 0.327 (p < 0.05) |
0.496 (p < 0.001) |
0.591 (p < 0.001) |
0.536 (p < 0.001) |
0.469 (p < 0.001) |
0.591 (p < 0.001) |
0.565 (p < 0.001) |
| pNN50 | – | – | – | – | 0.588 (p < 0.001) |
0.658 (p < 0.001) |
0.674 (p < 0.001) |
| Pearson correlation coefficient* | |||||||
| lnSDNN | 0.509 (p < 0.001) |
0.564 (p < 0.001) |
0.626 (p < 0.001) |
0.730 (p < 0.001) |
0.735 (p < 0.001) |
0.740 (p < 0.001) |
0.811 (p < 0.001) |
| Cliff’s delta | |||||||
| SDNN | 0.220 | 0.350 | 0.435 | 0.332 | 0.052 | 0.279 | 0.158 |
| RMSSD | 0.094 | 0.200 | 0.145 | 0.109 | 0.068 | 0.139 | 0.085 |
| pNN50 | – | – | – | – | 0.086 | 0.137 | 0.092 |
| Cohen’s d | |||||||
| lnSDNN | 0.319 | 0.648 | 0.723 | 0.512 | 0.086 | 0.460 | 0.240 |
Note:
*
Statistically significant correlation (applied Bonferroni–Holm correction); 10s-1, 10s-2, and 10s-3 denote the first, second, and third group, of 10 s recordings, 30s-1 and 30s-2 the first and second group, of 30 s recordings, 60s the group of 60 s recordings, avg10s the average of all 10 s recordings, and avg30s the average of all 30 s recordings.