Figure 11. Participants’ responses to questions related to usability of Tongue Drive System (TDS) and sip-and-puff (SnP) (factor 1: PQ13– PQ20), satisfaction with TDS (factor 2: PQ21 and PQ22), and performance comparison with current assistive technology (AT) (factor 3: PQ23–PQ25). Error bars represent standard error. PC = personal computer, PQ = poststudy system usability questionnaire question, PW = powered wheelchair.