Figure 1. Estimated probability of having a normal SLST as a function of UPDRS-III score. Plotted is the estimated probability from the logistic regression model of being in the high SLST time group (i.e. cluster 2) as a function of UPDRS-III score. Only cluster 1, and not cluster 2, has an average SLST time that is significantly lower than that of the published age-matched normative data [6]. Thus, the probability of having a normal SLST time decreases with increasing UPDRS-III scores.