what is a plus minus stat in hockey for an nhl player

Gary Aldcorn had a plus/minus of +11 in his career.

	NAME	+/-	GP	G	A	P	PIM	PPG	PPA	SHG	SHA	GWG	S	S%
1	Gary Aldcorn G. Aldcorn	+11	140	26	38	64	60	1	3	0	1	4	233	11.2
2	Al Arbour A. Arbour	+62	407	8	35	43	367	1	0	0	4	1	180	4.4
3	Bob Armstrong B. Armstrong	-38	132	7	25	32	188	1	4	0	2	1	216	3.2
4	George Armstrong G. Armstrong	+101	746	181	271	452	235	34	57	7	12	27	1,748	10.4
5	Ralph Backstrom R. Backstrom	+71	963	260	338	598	372	30	40	4	3	38	2,460	10.6
6	Earl Balfour E. Balfour	+1	138	6	8	14	20	0	0	3	2	1	144	4.2
7	Murray Balfour M. Balfour	+8	301	66	89	155	383	10	9	0	0	7	586	11.3
8	Dave Balon D. Balon	+45	777	192	222	414	607	35	38	4	5	35	1,464	13.1
9	Stan Baluik S. Baluik	-2	7	0	0	0	2	0	0	0	0	0	7	0.0
10	Doug Barkley D. Barkley	+56	250	24	80	104	382	6	17	0	2	1	748	3.2
11	Jimmy Bartlett J. Bartlett	-23	107	23	13	36	143	2	1	1	0	0	197	11.7
12	Andy Bathgate A. Bathgate	-60	686	211	408	619	354	42	151	1	0	21	2,461	8.6
13	Bob Baun B. Baun	+139	826	35	165	200	1,274	1	13	0	2	3	1,176	3.0
14	Jean Beliveau J. Beliveau	+117	748	299	484	783	543	105	173	0	0	50	2,627	11.4
15	Leo Boivin L. Boivin	-212	728	52	175	227	620	8	22	3	5	5	1,344	3.9
16	Marcel Bonin M. Bonin	+50	157	40	83	123	143	10	16	0	0	7	331	12.1
17	Jack Bownass J. Bownass	-6	41	2	5	7	38	0	0	0	0	0	39	5.1
18	Carl Brewer C. Brewer	+185	533	22	177	199	895	0	34	3	6	2	803	2.7
19	Johnny Bucyk J. Bucyk	-7	1,299	500	727	1,227	343	154	268	4	0	78	3,087	16.2
20	Charlie Burns C. Burns	-81	679	97	187	284	224	4	15	16	17	13	1,073	9.0
21	Dave Creighton D. Creighton	-3	14	1	5	6	4	0	1	0	0	1	23	4.3
22	Joe Crozier J. Crozier	+3	5	0	3	3	2	0	0	0	0	0	7	0.0
23	Barry Cullen B. Cullen	-6	54	4	9	13	23	0	1	0	0	1	52	7.7
24	Brian Cullen B. Cullen	-1	106	19	40	59	12	7	10	0	0	1	151	12.6
25	Ian Cushenan I. Cushenan	-13	22	0	1	1	26	0	0	0	0	0	8	0.0