Table 7.

Degrees of freedom (DOF), variance explained, −2 × log(likelihood) – which is sometimes called deviance and was calculated using the natural log – and Bayesian information criteria (BIC) scores are shown for the four different models presented herein.

Name	DOF	% variance explained	−2 log(L)	BIC
All subjects (N = 105)
Mean	5	–	−4.02	27.29
Linear regression	10	12.10	−71.8	−9.21
Simultaneous 2-segment	11	20.70	−125.8	−56.95
Independent 2-segment	15	20.90	−126.7	−32.85
Passed balance test (N = 79)
Mean	5	–	−4.03	25.86
Linear regression	10	7.20	−33.6	26.15
Simultaneous 2-segment	11	20.10	−92.6	−26.79
Independent 2-segment	15	20.30	−93.6	−3.92

The simplest model simply calculates the mean (e.g., Table 1), ignoring age variations, and provides a standard statistical baseline for the three other models. The linear regression model (Table 5) has 10 fit parameters – a slope and intercept for each of the 5 motion directions. The independent 2-segment model has 15 fit parameters – a baseline, age cutoff, and slope for each of our 5 threshold measures reported herein. The simultaneous 2-segment model has 11 fit parameters – a single age cutoff as well as a baseline measure and slope for each of 5 threshold measures. The BIC was the smallest (best) for the 11-parameter model both for all subjects and for subjects who passed the balance test.