Previous Next

In the form designer, click + Add hidden field, then choose sensor_statistic as the field type.

sensor_statistic: summarize device sensor meta-data.

Platform limitations

Only SurveyCTO Collect on Android supports this field type. It's not supported on iOS or the web. More about platform limitations...

In order to make sensor meta-data available in a safe and convenient format for monitoring and quality control, SurveyCTO offers a series of non-personally-identifiable summary statistics for each type of sensor. While the underlying streams of sensor data are higher-frequency, all summary statistics are based on a lower-frequency – but more uniform – stream of means. Specifically, SurveyCTO calculates a mean value for each one-second period, and then calculates the overall summary statistic based on those means. For a three-minute interview, for example, the statistic will be calculated based on 180 means, one for each second of collected sensor data.

To learn all about sensor meta-data, please see Experimental: Using sensor meta-data to enhance quality-control efforts.

SurveyCTO includes support for these basic sensor statistics:

1. sensor_statistic mean_light_level - mean light level measured in lux, as reported by the device's ambient light sensor.
2. sensor_statistic min_light_level - minimum light level measured in lux, as reported by the device's ambient light sensor.
3. sensor_statistic max_light_level - maximum light level measured in lux, as reported by the device's ambient light sensor.
4. sensor_statistic sd_light_level - standard deviation of light level measured in lux, as reported by the device's ambient light sensor.
5. sensor_statistic mean_movement - mean linear acceleration measured in m/s², as reported by the device's linear acceleration sensor and gyroscope sensor.
6. sensor_statistic min_movement - minimum linear acceleration measured in m/s², as reported by the device's linear acceleration sensor and gyroscope sensor.
7. sensor_statistic max_movement - maximum linear acceleration measured in m/s², as reported by the device's linear acceleration sensor and gyroscope sensor.
8. sensor_statistic sd_movement - standard deviation of linear acceleration measured in m/s², as reported by the device's linear acceleration sensor and gyroscope sensor.
9. sensor_statistic mean_sound_level - mean sound level measured in dB, as calculated from the device microphone.
10. sensor_statistic min_sound_level - minimum sound level measured in dB, as calculated from the device microphone.
11. sensor_statistic max_sound_level - maximum sound level measured in dB, as calculated from the device microphone.
12. sensor_statistic sd_sound_level - standard deviation of sound level measured in dB, as calculated from the device microphone.
13. sensor_statistic mean_sound_pitch - mean sound pitch measured in Hz, as calculated from the device microphone.
14. sensor_statistic min_sound_pitch - minimum sound pitch measured in Hz, as calculated from the device microphone.
15. sensor_statistic max_sound_pitch - maximum sound pitch measured in Hz, as calculated from the device microphone.
16. sensor_statistic sd_sound_pitch - standard deviation of sound pitch measured in Hz, as calculated from the device microphone.

And also these inference statistics:

1. sensor_statistic pct_light_level_between - percentage of time the light level was between x and y, where the appearance column includes "min=x;max=y" to specify the x and y (see this Wikipedia topic for more about lux light levels, but exact ranges will depend on your device and setting; use a sensor_stream field to see what ranges of values are captured for you, before deciding on a specific range to use).
2. sensor_statistic pct_sound_level_between - percentage of time the sound level was between x and y, where the appearance column includes "min=x;max=y" to specify the x and y (see this webpage for more about decibel sound levels, but exact ranges will depend on your device and setting; use a sensor_stream field to see what ranges of values are captured for you, before deciding on a specific range to use).
3. sensor_statistic pct_sound_pitch_between - percentage of time the estimated pitch was between x and y, where the appearance column includes "min=x;max=y" to specify the x and y (exact ranges will depend on your device and setting; use a sensor_stream field to see what ranges of values are captured for you, before deciding on a specific range to use).
4. sensor_statistic pct_movement_between - percentage of time linear acceleration was between x and y, where the appearance column includes "min=x;max=y" to specify the x and y (exact ranges will depend on your device and setting; use a sensor_stream field to see what ranges of values are captured for you, before deciding on a specific range to use).
5. sensor_statistic pct_quiet - percentage of time quiet. This is the same as using pct_sound_level_between with "max=25" in the appearance.
6. sensor_statistic pct_still - percentage of time the device was still. This is the same as using pct_movement_between with "max=0.15" in the appearance.
7. sensor_statistic pct_moving - percentage of time the device was moving. This is the same as using pct_movement_between with "min=1.5" in the appearance.
8. sensor_statistic pct_conversation - percentage of time conversation seemed to be happening. This statistic is particularly experimental, and its voice activity detection algorithm may or may not work well for you. Before you rely on it too heavily, test it out, and consider recording audio audits so that you can listen for yourself, to verify submissions flagged for, e.g., too little apparent conversation.

In the spreadsheet form definition:

type	name	appearance
sensor_statistic mean_sound_level	fieldname
sensor_statistic pct_quiet	fieldname
sensor_statistic pct_conversation	fieldname
sensor_statistic pct_light_level_between	fieldname	min=#;max=#

(The above table only includes a few representative examples. See the full list of options further above.)

Previous Next