Table 3.

Overall deviation of fitness tracker heart rate measurements and the clinical gold standard.

	Philips	Apple	Fitbit	Garmin	Withings
Valid measurement points, n	333	327	308	332	330
Failed measurements, n	3	9	28	4	6
CDRa (%)	0.89	2.67	8.33	1.19	1.79
MAEb	0.92	1.59	2.31	2.47	1.71
MAPEc (%)	1	2	4	3	2
Bias (95% CI)	–0.25 (–0.42 to –0.08)	0.36 (0.09 to 0.63)	0.77 (0.28 to 1.26)	–1.21 (–1.65 to –0.77)	0.05 (–0.28 to 0.40)

^aCDR: cumulative dropout rate.

^bMAE: median absolute error.

^cMAPE: mean absolute percentage error.