Table 2.

Accuracy (mean difference between target location and observed point in degrees of visual angle) and precision (RMS noise and standard deviation in degrees of visual angle) with real data. Data were obtained from the custom-built eye tracker and an EyeLink 1000 Plus system, using five fixation targets (see Figure 6), with a viewing time of 1.5 seconds each. Fixation points spanned a range from -4.2 to 4.2 degrees horizontally, and -3.8 to 3.8 vertically around the display center. The numbers in parentheses denote standard deviations across repeated measurements.

	Custom-built eye tracker	EyeLink 1000 Plus
Precision (RMS)
horizontal	0.0457 (0.0301)	0.0202 (0.0297)
vertical	0.0467 (0.0310)	0.0271 (0.0403)
Precision (standard deviation)
horizontal	0.1953 (0.1861)	0.1746 (0.1972)
vertical	0.1984 (0.1812)	0.2160 (0.1944)
Accuracy
horizontal	0.3858 (0.2488)	0.5504 (0.3051)
vertical	0.4750 (0.4718)	1.0192 (0.7170)