Table 2.

Balance of preoperative covariates for unweighted and weighted data (mean values)

	Unweighted				Weighted
Laparoscopic	Open	ASAM	p	Laparoscopic	Open	ASAM	p
Age	63.36	60.49	0.25	0.04	63.05	61.35	0.15	0.25
Sex(female)	0.40	0.33	0.16	0.17	0.38	0.34	0.08	0.55
CEA	35.24	51.74	−0.11	0.37	35.96	54.92	−0.13	0.31
Major resection	0.27	0.69	−0.84	0.00	0.42	0.54	−0.23	0.10
Difficult location	0.34	0.56	−0.43	0.00	0.42	0.46	−0.09	0.52
Bilateral	0.11	0.27	−0.41	0.00	0.14	0.22	−0.21	0.13
Maximum diameter	32.29	41.85	−0.34	0.00	34.13	38.32	−0.16	0.23
Number of lesions	1.47	2.13	−0.48	0.00	1.60	1.88	−0.22	0.10
Primary lesion:
Mod differentiated	0.77	0.64	0.31	0.04	0.75	0.66	0.20	0.39
Poorly differentiated	0.19	0.27	−0.19		0.20	0.27	−0.16
Well differentiated	0.03	0.09	−0.29		0.04	0.07	−0.10
T1/T2	0.27	0.23	0.09	0.72	0.26	0.23	0.07	0.74
T3	0.53	0.56	−0.06		0.55	0.54	0.01
T4	0.20	0.21	−0.03		0.19	0.23	−0.10
N0	0.42	0.35	0.16	0.00	0.38	0.36	0.05	0.40
N1	0.30	0.49	−0.44		0.34	0.46	−0.24
N2	0.19	0.14	0.12		0.20	0.14	0.14
N3	0.09	0.01	0.26		0.08	0.04	0.14
Years from primary
0	0.03	0.02	0.07	0.39	0.03	0.02	0.08	0.60
1	0.47	0.36	0.22		0.47	0.40	0.14
2	0.27	0.34	−0.17		0.26	0.33	−0.16
3	0.09	0.09	0.01		0.09	0.08	0.04
4	0.04	0.07	−0.16		0.04	0.07	−0.18
5	0.10	0.12	−0.07		0.11	0.11	0.02
Previous chemotherapy	0.28	0.34	−0.13	0.28	0.27	0.36	−0.19	0.18

ASAM, average standardised absolute mean difference.