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Usability Evaluation of Touchless Mouse Based on Infrared Proximity Sensing

Young Sam Ryu, Do Hyong Koh, Dongseok Ryu, and Dugan Um

Journal of Usability Studies, Volume 7, Issue 1, November 2011, pp. 31 - 39

Article Contents


Results

The following sections discuss the Fitt’s law test and the post-test survey.

Fitts’ Law Test

The following sections discuss the performance of each device based on the results from the Fitts’ law tests in terms of completion time, throughput, and error rate.

Completion Time

Because targets were selected (clicked) automatically following a cursor dwell-time of two seconds, two seconds were subtracted from each completion time to provide a fair comparison. The test results showed that the average completion time of the multi-directional Fitts’ Law discrete tasks with conventional mouse was 0.97 seconds (SD=0.22), while the average completion time with the T-less mouse for the first trial was 3.45 seconds (SD=1.14), which was reduced down to 3.09 seconds (SD=1.01) in the second trial (Figure 4). The difference in completion times between the three types of trials was statistically significant F(2,34)=57.71, p<0.0001. Post-hoc analyses using the Scheffé criterion for significance indicated that T-less first trial completion time was significantly longer than for a conventional mouse, p<0.05, but not significantly longer than T-less second trial, p>0.05.

Figure 4

Figure 4. Average completion time for three types of trials

Throughput

The throughput from the multi-directional Fitts’ Law discrete tasks with a conventional mouse was 2.85 bps (SD=0.41), while the throughput with the first T-less mouse trial was 0.72 bps (SD=0.26), and with the second T-less mouse trial was 0.83 seconds (SD=0.25), respectively (Figure 5). The difference in throughput between the three trial types was statistically significant, F(2,34)=298.63, p<0.0001. Post-hoc analyses using the Scheffé criterion for significance indicated that the conventional mouse throughput was significantly higher than both T-less trials, p<0.05, but throughput of the T-less second trial was not significantly higher than the T-less first trial, p>0.05.

Figure 5

Figure 5. Throughput for each type of trial

Error Rate

The error rate was computed as the number of error clicks divided by the total number of clicks, where an error click was defined as a click outside of the target. The average error rate with the conventional mouse was 2.09% (SD=5.00), while the error with the T-less first trial was 5.79% (SD=8.01), and with the T-less second trial was 4.03% (SD=7.28), respectively (Figure 6). However, the differences in error rate between the three types of trials were not statistically significant, F(2,34)=1.80, p=0.1810. Post-hoc analyses using the Scheffé criterion for significance also indicated that there were no significant differences in error rate among the three types of trials. It should be noted that 14 participants out of 18 with the conventional mouse committed no error at all, 10 participants with the T-less first trial committed no error, and 12 participants with the T-less second trial committed no error.

Figure 6

Figure 6. Error rate for each type of trial

Post-Test Survey

In the post-test survey about the T-less mouse, all questions were rated on a 7-point Likert scale. Among wrist, arm, and shoulder fatigue selections, the participants rated wrist fatigue highest and shoulder fatigue lowest. Only 2 out of 18 participants preferred T-less mouse to conventional mouse. However, 15 out of 18 participants agreed that the T-less mouse could be a useful alternative to replace a conventional mouse in circumstances where a conventional mouse cannot be used. Other ratings did not show any significantly skewed opinion from the middle point of the 7-point scale. The summary of the average ratings (center points of the bar) and standard deviation (half length of the bars) of all questions is provided in Table 1. 

Table 1. Summary of the Post-Test Ratings of the T-less Mouse

Table 1

 

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