Figure 2.

Bland-Altman plots with comparison of step counts in three validation approaches: internal (a.), manual (b.), and wearable (c.). The horizontal axis indicates a mean step count from the two body locations (a.), estimated steps and manually counted ground truth (b.), and estimated steps and step counts obtained from Fitbit (c.). The vertical axis indicates a difference between step counts from the two methods. Blue solid lines indicate mean bias while dashed red lines indicate ±95% limits of agreement calculated as ±1.96 of standard deviations of the differences between the two methods.