Table 1.

Performance classification for Pearson’s correlation coefficient (r) and confidence index (c) [33,35].

Correlation Coefficient (r)	Classification	Confidence Index (c)	Classification
>0.99	Perfect	>0.85	Excellent
0.91–0.99	Almost perfect	0.76–0.85	Very good
0.71–0.90	Very high	0.66–0.75	Good
0.51–0.70	High	0.61–0.65	Satisfactory
0.31–0.50	Moderate	0.51–0.60	poor
0.11–0.30	Low	0.41–0.50	Bad
<0.10	Very low	<0.40	Very bad