Hi,
Sorry for the late reply
1. Participants run the experiment in different conditions (different machines, different browsers, different number of tabs and programs open) which affect performance, hence the important variability in the intervals. The best you can do is to invite all your participants to use the same browser and close all tabs and programs that they can before taking your experiment
2. When the data says (0,0) it means the eye tracker estimated that the gaze did not fall on either left of right. This can happen if the tracker estimated that the gaze was somewhere else on the page, somewhere else on the screen (for example the browser’s address bar) or if the participant closed their eyes, for example; all those remain estimates though, maybe the participant was indeed looking at either left or right but tracker got it wrong
3. I’m not sure I understand this question
Jeremy