Quantifying sources of variability in gait analysis

Measurements from gait analysis are affected by many sources of variability. Schwartz et al. [1] illustrated an experimental design and methods to estimate these variance components. However, the derivation contains errors which could severely bias the estimation of some components. Therefore, in this paper, we presented correction to this method using ANOVA and Likelihood methods. Furthermore, we demonstrated how commonly used reliability indices like CMC and ICC may be derived from the variance components. We advocate the use of the variance components, in preference to reliability indices, because the variance components are easier to interpret, with understandable units.