what is the formula used to find variable d_gpa

CaseNum	ADDSC	Gender	Repeat	IQ	EngL	EngG	GPA	SocProb	Dropout	d_GPA
1	45	1	0	111	2	3	2.6	0	0	1
2	50	1	0	102	2	3	2.75	0	0	1
3	49	1	0	108	2	4	4	0	0	1
4	55	1	0	109	2	2	2.25	0	0	0
5	39	1	0	118	2	3	3	0	0	1
6	68	1	1	79	2	2	1.67	0	1	0
7	69	1	1	88	2	2	2.25	1	1	0
8	56	1	0	102	2	4	3.4	0	0	1
9	58	1	0	105	3	1	1.33	0	0	0
10	48	1	0	92	2	4	3.5	0	0	1
11	34	1	0	131	2	4	3.75	0	0	1
12	50	2	0	104	1	3	2.67	0	0	1
13	85	1	0	83	2	3	2.75	1	0	1
14	49	1	0	84	2	2	2	0	0	0
15	51	1	0	85	2	3	2.75	0	0	1
16	53	1	0	110	2	2	2.5	0	0	1
17	36	2	0	121	1	4	3.55	0	0	1
18	62	2	0	120	2	3	2.75	0	0	1
19	46	2	0	100	2	4	3.5	0	0	1
20	50	2	0	94	2	2	2.75	1	1	1
21	47	2	0	89	1	2	3	0	0	1
22	50	2	0	93	2	4	3.25	0	0	1
23	44	2	0	128	2	4	3.3	0	0	1
24	50	2	0	84	2	3	2.75	0	0	1
25	29	2	0	127	1	4	3.75	0	0	1
26	49	2	0	106	2	3	2.75	0	0	1
27	26	1	0	137	2	3	3	0	0	1
28	85	1	1	82	3	2	1.75	1	1	0
29	53	1	0	106	2	3	2.75	1	0	1
30	53	1	0	109	2	2	1.33	0	0	0
31	72	1	0	91	2	2	0.67	0	0	0
32	35	1	0	111	2	2	2.25	0	0	0
33	42	1	0	105	2	2	1.75	0	0	0
34	37	1	0	118	2	4	3.25	0	0	1
35	46	1	0	103	3	2	1.75	0	0	0
36	48	1	0	101	1	3	3	0	0	1
37	46	1	0	101	3	3	3	0	0	1
38	49	1	1	95	2	3	3	0	0	1
39	65	1	1	108	2	3	3.25	0	0	1
40	52	1	0	95	3	3	2.25	1	0	0
41	75	1	1	98	2	1	1	0	1	0
42	58	1	0	82	2	3	2.5	0	1	1
43	43	2	0	100	1	3	3	0	0	1
44	60	2	0	100	2	3	2.4	0	0	0
45	43	1	0	107	1	2	2	0	0	0
46	51	1	0	95	2	2	2.75	0	0	1
47	70	1	1	97	2	3	2.67	1	1	1
48	69	1	1	93	2	2	2	0	0	0
49	65	1	1	81	1	2	2	0	0	0
50	63	2	0	89	2	2	1.67	0	0	0
51	44	2	0	111	2	4	3	0	0	1
52	61	2	1	95	2	1	1.5	0	1	0
53	40	2	0	106	2	4	3.75	0	0	1
54	62	2	0	83	3	1	0.67	0	0	0
55	59	1	0	81	2	2	1.5	0	0	0
56	47	2	0	115	1	4	4	0	0	1
57	50	2	0	112	2	3	3	0	0	1
58	50	2	0	92	2	3	2.33	0	0	0
59	65	2	0	85	2	2	1.75	0	0	0
60	54	2	0	95	3	2	3	0	0	1
61	44	2	0	115	2	4	3.75	0	0	1
62	66	2	0	91	2	4	2.67	1	1	1
63	34	2	0	107	1	4	3.5	0	0	1
64	74	2	0	102	2	0	0.67	0	0	0
65	57	2	1	86	3	3	2.25	0	0	0
66	60	2	0	96	1	3	3	1	0	1
67	36	2	0	114	2	3	3.5	0	0	1
68	50	1	0	105	2	2	1.75	0	0	0
69	60	1	0	82	2	1	1	0	0	0
70	45	1	0	120	2	3	3	0	0	1
71	55	1	0	88	2	1	1	0	1	0
72	44	1	0	90	1	3	2.5	0	0	1
73	57	2	0	85	2	3	2.5	0	0	1
74	33	2	0	106	1	4	3.75	0	0	1
75	30	2	0	109	1	4	3.5	0	0	1
76	64	1	0	75	3	2	1	1	0	0
77	49	1	1	91	2	3	2.25	0	0	0
78	76	1	0	96	2	2	1	0	0	0
79	40	1	0	108	2	3	2.5	0	0	1
80	48	1	0	86	2	3	2.75	0	0	1
81	65	1	0	98	2	2	0.75	0	0	0
82	50	1	0	99	2	2	1.3	0	0	0
83	70	1	0	95	2	1	1.25	0	0	0
84	78	1	0	88	3	3	1.5	0	0	0
85	44	1	0	111	2	2	3	0	0	1
86	48	1	0	103	2	1	2	0	0	0
87	52	1	0	107	2	2	2	0	0	0
88	40	1	0	118	2	2	2.5	0	0	1