Table 3.

The number of repeat measurements required of the APP angle

Observer	A	B	C	A and B	B and C	C and A	All
Difference from true value* (degrees)	0.29 ± 1.42	−0.03 ± 1.76	0.10 ± 1.57	0.13 ± 1.58	0.04 ± 1.66	0.19 ± 1.49	0.11 ± 1.59
Range (degrees)	−2.8, 3.7	−4.8, 4.0	−3.2, 3.5	−4.8, 4.0	−4.8, 4.0	−3.2, 3.7	−4.8, 4.0
ICC	0.803**	0.705**	0.829**	0.883	0.872	0.808	0.897
95% CI	0.707, 0.867	0.577, 0.808	0.744, 0.893	0.793, 0.934	0.774, 0.928	0.649, 0.888	0.827–0.940
p value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
k value	–	1.6	–	–	–	–	–

APP = anterior pelvic plane; ICC = intraclass correlation coefficient; CI = confidence interval; k = number of repeat measurements required, * mean ± standard deviation, ** single measurement.