How is the sample % calculated in Tobii Pro  Studio and what can I use it for?

what is the sample % on my recording?

From Tobii Pro Studio 3.4, two samples percentages are available.

  • Gaze Samples: The percent is calculated by dividing the number of eye tracking samples with usable gaze data that were correctly identified, by the number of attempts. 100% means that one or both eyes were found throughout the recording. 50% means that one eye or both eyes were found for half of the recording duration. Note that the eyes cannot be found when a person is looking away from the screen; this will result in a lower percentage. If the test is performed so that the participant is asked questions during the recording and occasionally looks at a test leader, an alternative method for determining the quality of the recording should be considered. (Data collected using a Tobii Studio version lower than 3.4.1 will not have a value in this column. This is because this measure was introduced in version 3.4.1 and it is calculated at the time of recording which means that older recordings will not have it.)
  • Weighted Gaze Samples (previously called Samples): The percent is calculated by dividing the number of eye tracking samples that were correctly identified, by the number of attempts. This value is weighted based on if both or just one eye was detected in a sample. 100% means that both eyes were found throughout the recording. 50% means that one eye was found for the full recording or both eyes during half the time. Note that the eyes cannot be found when a person is looking away from the screen; this will result in a lower percentage. If the test is performed so that the participant is asked questions during the recording and occasionally looks at a test leader, an alternative method for determining the quality of the recording should be considered.

Those measures can be used to evaluate the quantity of valid gaze samples collected by the eye tracker.

A low sample % can reflect many things: inaccurate configuration, light interferences, participant more difficult to track or just a task drawing the participant attention from the eye tracker track box.