Darcy Ummels

The validation of a pocket worn activity tracker | 99 5 Coefficient (absolute agreement, two ‐ way random) and Bland ‐ Altman plots with limits of agreement. It was hypothesized that there was a strong correlation between observers ( r ≥ 0 .90) in order to guarantee a robust gold standard. 37 Validation To check for outliers in the data of MOX Miss ‐ Activity , MOX Annegarn , activPAL, Fitbit versus the video observations regarding the variables step count, dynamic, standing, and sedentary time the data were transformed to z ‐ scores and Bland ‐ Altman plots were visually inspected. In case of outliers, pairwise deletion was applied. For step count, dynamic, standing, and sedentary time the mean (95% CI), mean difference, the percentage error (PE), the absolute percentage error (APE), and the smallest detectable change (SDC) were used to gain insight into the algorithm’s and activity trackers’ performance compared to video observations. (1) (2) (3) Formula 1 and 2 show the calculation of PE and APE for each variable. A PE or APE of less than 10% was considered acceptable. 38 Formula 3 shows the calculation of SDC. The level of agreement between step count, dynamic, standing, and sedentary time and the video observations were examined by a Bland ‐ Altman plot with their limits of agreement. 39 Pearson correlation coefficients were calculated to gain insight into the relationship between the MOX MissActivity , MOX Annegarn , activPAL, Fitbit versus the video observations regarding the variables step count, dynamic, standing, and sedentary time. It was hypothesised that there would be at least a substantial correlation ( r ≥ 0.60). 37 A paired sample t ‐ test was used to determine large systematic differences between the MOX MissActivity , MOX Annegarn , activPAL, Fitbit versus the video observations regarding the variables step count, dynamic, standing, and sedentary time. A p ‐ value below 0.05 was considered to be statistically significant. Additionally the sensitivity, specificity and accuracy are calculated. Variable Gold standard PE = * 100 Variable Gold standard Variable Actvity tracker APE = * 100 Variable Activity tracker Variable Gold standard Variable Gold standard SDC = 1.96 * 2 * standard error measurement