An Improved Nonequidistant Grey Model Based on Simpson Formula and Its Application

Table 6

Simulative and predictive values by the competitive models in Case 2.

Time	Data	GM (1, 1)		NGM (1, 1, k)		NEGM (1, 1, t^2)		INEGM (1, 1, t^2)
		Value	APE (%)	Value	APE (%)	Value	APE (%)	Value	APE (%)
In-sample
1	9.28	9.28	0.00	9.28	0.00	9.28	0.00	9.28	0.00
25	10.71	10.88	1.59	10.75	0.37	10.75	0.37	10.72	0.56
53	11.31	11.19	1.06	11.27	0.35	1.30	0.09	11.30	0.11
83	11.64	11.54	0.86	11.68	0.34	11.67	0.26	11.66	0.16
116	12.00	11.93	0.58	12.00	0.00	11.97	0.25	12.28	0.39
147	12.23	12.34	0.90	12.22	0.08	12.24	0.08	12.28	0.39
Out-of-sample
177	13.05	12.75	2.30	12.36	5.29	12.48	5.29	12.56	3.72
237	13.16	13.38	1.67	12.50	5.02	12.83	5.02	12.99	1.31
269	13.61	14.04	3.16	12.58	7.57	13.18	7.57	13.42	1.40
355	13.94	14.96	7.32	12.63	9.40	13.63	9.40	13.97	0.24