Table 2. Correlation and agreement between step counts derived from Fitbit and Actigraph.
| Comparison | r [95% CI] | CCC [95% CI] |
|---|---|---|
| Scripted tasks | ||
| Manual vs Act(Stand)a | 0.97 [0.77–0.99] | 0.68 [0.37–0.82] |
| Manual vs Act(LFE)a | 0.98 [0.78–0.99] | 0.73 [0.13–0.84] |
| Act(Stand) vs Act(LFE)a | 0.97 [0.85–0.99] | 0.60 [0.06–0.76] |
| Fitbit vs. Manual | 0.92 [0.63–0.98] | 0.66 [0.14–0.80] |
| Fitbit vs. Act(Stand) | 0.92 [0.65–0.97] | 0.55 [0.08–0.72] |
| Fitbit vs. Act(LFE) | 0.93 [0.65–0.98] | 0.65 [0.24–0.77] |
| Free living, Epoch level | ||
| Act(Stand) vs Act(LFE) a | 0.27 [0.24–0.30] | 0.03 [0.02–0.04] |
| Fitbit vs. Act(Stand) | 0.22 [0.19–0.25] | 0.04 [0.03–0.05] |
| Fitbit vs. Act(LFE) | 0.22 [0.19–0.25] | 0.03 [0.02–0.05] |
| Free living, Daily level | ||
| Act(Stand) vs Act(LFE) a | 0.88 [0.84–0.91] | 0.15 [0.11–0.20] |
| Fitbit vs. Act(LFE) | 0.82 [0.78–0.87] | 0.33 [0.22–0.43] |
| Fitbit vs. Act(Stand) | 0.80 [0.75–0.85] | 0.44 [0.32–0.57] |
| Free living, Average level | ||
| Act(Stand) vs Act(LFE) a | 0.89 [0.78–0.94] | 0.27 [0.16–0.37] |
| Fitbit vs. Act(LFE) | 0.86 [0.74–0.93] | 0.50 [0.34–0.63] |
| Fitbit vs. Act(Stand) | 0.82 [0.67–0.90] | 0.65 [0.47–0.77] |
a Comparison between two criterion measures
Act: Actigraph; Stand: Standard; LFE: Low frequency extension; r: Pearson correlation coefficient; CI: confidence interval; CCC: Lin’s Concordance correlation coefficient