Table 3.

Examples of sensor features.

Device and sensor		Extracted feature
Smartphone
	Audio	Percentage of time with voice, noise, or silence; minimum, maximum, mean, or SD of voice energy
	Bluetooth	Mean or total number of Bluetooth scans
	Wi-Fi	Number of unique Wi-Fi hotspots detected
	Location	Location variance; percentage of time staying at home; number of visits; time spent at green areas, athletic areas, academic areas, or outside campus
	Phone usage	Minutes interacting with phone; minimum, maximum, mean, or SD length of interaction periods
Fitbit
	Sleep	Minutes asleep, awake, or restless; minimum, maximum, or mean length of asleep, awake, or restless periods
	Steps	Total number of steps; minimum, maximum, mean, and total length of active or sedentary periods
	Calories	Minimum, maximum, mean, or total calories burned; minimum, maximum, mean, or total decrease in 5-minute calories burned