Table 5.

Classification accuracy metrics for identification of moderate intensity (≥ 3 METs) using candidate heuristic speed thresholds expressed in commonly used speed units

	Sensitivity (%)	Specificity (%)	Accuracy (%)	PPV (%)	NPV (%)	True positives n (%)	True negatives n (%)	False positives n (%)	False negatives n (%)
2.5 mph	91.4	45.2	79.8	83.3	63.6	170 (68.5%)	28 (11.3%)	34 (13.7%)	16 (6.5%)
3 mph	46.2	95.2	58.5	96.6	37.1	86 (34.7%)	59 (23.8%)	3 (1.2%)	100 (40.3%)
4.5 km/h	66.1	75.8	68.5	89.1	42.7	123 (49.6%)	47 (19.0%)	15 (6.0%)	63 (25.4%)
5 km/h	36.6	98.4	52.0	98.6	34.1	68 (27.4%)	61 (25.0%)	1 (0.4%)	118 (47.6%)

Note: The above values were calculated using the whole sample (i.e., not age specific). The optimal speed threshold for the whole sample is 1.28 m/s, and was converted into 2.87 mph or 4.61 km/h. We herein compared the classification metrics of two sets of candidate heuristic thresholds in different units for ease of interpretation. Abbreviations: METs, metabolic equivalents (1 MET = 3.5 mL/kg/min). NPV, negative predictive value; PPV, positive predictive value.