Reproducibility of natural head position measured with an inclinometer

Sagittal (pitch) and transversal (roll) natural head position (NHP) was measured once in 20 subjects, 18 to 24 years of age, with an inclinometer; the measurements were repeated 2 years later. The method error (reproducibility) after 2 years was 1.1degrees for sagittal and transversal measurements. The mean change in NHP measurement was -0.3degrees for both measurements, and the variance was 1.21degrees (= 1.1(2)).