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.