Table 2. Binary classification tests for the single item measure versus accelerometer total MVPA (MVPA-total) and MVPA occurring in bouts (MVPA-bouts) for detecting increases in number of days ≥30 minutes MVPA from week one to week two.

	Detecting increases in number of days ≥30 min MVPA
	Single item vs accelerometer (MVPA-total)	Single item vs accelerometer (MVPA-bouts)
Participants in category (%)	59	64
Accuracy (%)	60.0 (49.1 to 70.2)	63.3 (52.5 to 73.3)
Sensitivity (%)	63.1 (50.2 to 74.7)	69.2 (56.6 to 80.1)
Specificity (%)	52.0 (31.3 to 72.2)	48.0 (21.1 to 68.7)
Positive predictive value (%)	77.4 (68.6 to 84.3)	77.6 (69.7 to 83.9)
Negative predictive value (%)	35.1 (24.9 to 47.0)	37.5 (25.8 to 50.9)