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

Table 3

Simulative and predictive values by the competitive models in Case 1.

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	78.60	78.60	0.00	78.60	0.00	78.60	0.00	78.60	0.00
3	78.40	79.06	0.84	78.67	0.34	78.67	0.35	78.52	0.16
5	80.30	79.65	0.81	79.83	0.58	80.08	0.27	80.19	0.14
8	80.70	80.39	0.38	80.77	0.09	80.67	0.04	80.67	0.03
10	81.10	81.15	0.06	81.37	0.33	81.66	0.08	81.15	0.03
12	81.50	81.75	0.31	81.67	0.21	81.55	0.06	81.52	0.03
15	82.10	82.03	0.08	81.91	0.23	82.03	0.08	81.99	0.13
Out-of-sample
17	82.60	82.51	0.10	82.07	0.64	82.52	0.10	82.47	0.16
19	82.80	83.29	0.59	82.15	0.79	82.90	0.13	82.84	0.05
22	83.70	83.92	0.26	28.21	1.78	83.39	0.37	83.31	0.46
25	83.80	84.70	1.08	82.26	1.84	83.97	0.20	83.88	0.10
29	84.00	85.65	1.97	82.28	2.04	84.64	0.77	84.54	0.64
31	84.70	86.78	2.46	82.30	2.84	85.22	0.62	85.11	0.48