Prewebinar survey DIF detection procedure for ordinal data based on adjacent category logit model with orthopedic surgeons as the reference and neurosurgeons as the focal group.
| Procedure | Statistic | P | Adjusted P |
| Endoscopic complex lumbar revision strategies | 2.5379 | 0.281 | 0.562 |
| Endoscopic debridement of grades 1–3 spondylolytic spondylolisthesis | 0.0649 | 0.968 | 0.988 |
| Posterior cervical endoscopic foraminotomy for disc herniation and bony stenosis | 0.0251 | 0.988 | 0.988 |
| Posterior endoscopic single and multilevel decompression of cervical spondylotic myelopathy | 4.3128 | 0.116 | 0.463 |
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.