. 2022 Jun 6;8(6):e09598. doi: 10.1016/j.heliyon.2022.e09598

Table 8.

Details of the statistical tests.

S/N	Abbreviation	Statistical test	Expression	Ideal value
1.	MBE	Mean bias error	$M B E = \frac{1}{2} \sum_{i = 1}^{n} ((O_{i} - P_{i}))$	Zero
2.	MPE	Mean percentage error	$M P E = \frac{1}{2} \sum_{i = 1}^{n} (\frac{(O_{i} - P_{i})}{O_{i}}) \times 100$	Zero
3.	RMSE	Root mean square error	$R M S E = \sqrt{\frac{1}{n} \sum_{i = 1}^{n} {(O_{i} - P_{i})}^{2}}$	Zero
4.	RRMSE	Relative root mean square error	$R R M S E = \frac{{[\frac{1}{n} \sum_{i = 1}^{n} {(O_{i} - P_{i})}^{2}]}^{1 / 2}}{\frac{1}{n} \sum_{i = 1}^{n} O_{a v e}}$	Zero
5.	R²	Coefficient of determination	$R^{2} = 1 - [\frac{\sum_{i = 1}^{n} {(O_{i} - P_{i})}^{2}}{\sum_{i = 1}^{n} {(O_{i} - O_{a v e})}^{2}}]$	One
6.	GPI	Global performance indicator [55], [56]	$G P I = \sum_{i = 1}^{5} α_{j} ({\bar{y}}_{i} - {\bar{y}}_{i j})$	Negative to positive