Table 4.

Postwebinar survey DIF detection procedure for ordinal data based on adjacent category logit model with surgeons from outside China as the reference vs those from China as the focal group l.

Procedure	Statistic	P	Adjusted P
Endoscopic complex lumbar revision strategies	11.9786	0.003	0.010
Endoscopic debridement of grades 1–3 spondylolytic spondylolisthesis	0.0476	0.976	0.976
Posterior cervical endoscopic foraminotomy for disc herniation and bony stenosis	5.3029	0.071	0.114
Posterior endoscopic single and multilevel decompression of cervical spondylotic myelopathy	4.9126	0.086	0.114

Abbreviation: DIF, differential item functioning.

Note. DIF likelihood ratio statistics are estimated by using difNLR and difORD function. The adjusted P values are calculated by likelihood ratio test using multiple comparison.