Table 5. Subgroup analysis of random error(mm) according to cervical spine level.

Variables	C1-2			C3-5			C6-7
	mean	SD	p-value	mean	SD	p-value	mean	SD	p-value
Translation
x	−2.01	2.96	0.004	−1.34	2.58	0.024	−1.33	2.86	0.040
y	1.45	14.6	0.646	1.38	14.71	0.665	0.39	14.42	0.902
z	−0.50	1.03	0.034	0.02	0.91	0.919	−0.18	0.81	0.314
Rotation
x	0.31	0.917	0.130	−0.09	0.33	0.203	−0.29	0.45	0.006
y	−0.46	0.591	0.001	−0.35	0.43	0.001	−0.20	0.35	0.013
z	−0.89	1.160	0.002	0.01	0.30	0.893	0.12	0.56	0.333