. 2018 Dec 21;1(8):e186040. doi: 10.1001/jamanetworkopen.2018.6040

Table 3. Percentage of Correctly Reidentified Matches at Different Time Resolutions of Partial Aggregation of Physical Activity Data.

Machine Learning Algorithm	Correctly Reidentified Matches, %
Machine Learning Algorithm	15 min	20 min	30 min	1 h	2 h	4 h	6 h	8 h	12 h	24 h
Adults in NHANES 2003-2004
Demographics only^a	81.1^b
Physical activity
Linear SVM^c	0	0	0	0.02	0	0.04	0	0.06	0.02	0.02
Random forest^a	5.97	5.93	6.52	5.61	4.24	2.14	1.14	0.74	0.23	0.23
Demographics and physical activity
Linear SVM^a	85.2	85.6	87.0	86.9	87.7	87.4	86.8	86.7	85.7	84.8
Random forest^a	94.3	94.9	94.5	94.0	93.0	91.7	91.3	90.6	89.0	87.0
Adults in NHANES 2005-2006
Demographics only^a	80.3^b
Physical activity
Linear SVM^c	0	0.02	0.02	0	0.02	0	0.02	0.02	0.02	0.02
Random forest	6.40^a	6.48^a	6.55^a	6.04^a	4.55^a	2.29^a	1.09^a	0.55^a	0.23^a	0.08^b
Demographics and physical activity
Linear SVM^a	84.5	84.8	84.7	85.1	86.3	86.1	85.9	85.5	85.0	83.1
Random forest^a	93.5	93.8	93.2	92.8	91.9	91.0	90.5	89.4	87.9	85.8
Children in NHANES 2003-2004
Demographics only^a	61.6^b
Physical activity
Linear SVM^c	0.08	0	0.04	0.04	0	0.04	0	0.08	0.04	0.04
Random Forest	11.1^a	10.5^a	11.0^a	7.83^a	4.45^a	1.98^a	0.95^a	0.58^a	0.37^a	0.04^b
Demographics and physical activity
Linear SVM^a	70.3	69.8	70.8	71.5	68.9	69.9	67.0	68.6	67.5	64.3
Random forest^a	87.2	87.4	87.1	84.8	83.1	80.0	78.6	76.9	73.8	70.2
Children in NHANES 2005-2006
Demographics only^a	59.4^b
Physical activity
Linear SVM^c	0.08	0	0.04	0.08	0	0.08	0.04	0	0.08	0
Random forest^a	10.6	11.5	10.0	7.17	4.25	1.81	1.02	0.91	0.32	0.32
Demographics and physical activity
Linear SVM^a	67.2	67.2	67.0	67.2	66.0	67.0	66.4	67.0	64.7	62.4
Random forest^a	84.8	85.5	84.4	82.6	80.3	78.2	75.9	74.5	70.9	67.3

Abbreviations: NHANES, National Health and Nutrition Examination Survey; SVM, support vector machine.

^{^a}

P < .001.

^{^b}

The demographics-only results are not subject to any time; thus, the same numbers are independent of the time columns

^{^c}

P > .99.