Table 2.

Prediction accuracy levels of GM (1,1) model

Accuracy Level	Accuracy Class	Test Criteria
		Posterior Error Ratio, C	Small Error Probability, p
1st level	Excellent	C ≤ 0.35	p ≥ 0.95
2nd level	Qualified	0.35 < C ≤ 0.50	0.95 > p ≥ 0.80
3rd level	Marginal	0.50 < C ≤ 0.65	0.80 > p ≥ 0.70
4th level	Unqualified	0.65 < C	0.70 > p