Impact of Speller Size on a Visual P300 Brain-Computer Interface (BCI) System under Two Conditions of Constraint for Eye Movement

Table 2

Different evaluation metrics used to analyse the three usability dimensions.

Effectiveness	(i) Classification accuracy and number of flashes required to select a symbol during calibration
	(ii) Error performance according to the online task
	(iii) P300 waveforms (amplitude and latency)
Efficiency	(i) NASA-TLX
	(ii) VAS fatigue
	(iii) Perception subjective questionnaires
Satisfaction	(i) A comparative questionnaire adapted from the SUS for six dimensions (favourite, complex, comfortable, stressful, controllable, and tiring)