# Sensing Performance of a Vibrotactile Glove for Deaf-Blind People
## 3 Results  
In this section, the performance of both groups is compared, starting with the trials after the initial training for understanding the system operation. The results achieved by the DBS in the extended trials are analysed according to the different stimulation parameters, i.e., the number of factors, the keying frequencies or the fingers involved. The performance is analysed in terms of the success rate. For the statistical analysis, normality is assumed in the populations. A normality test was not considered because of the low number of subjects and the high number of ties achieved during the trials, i.e., repeated values in the sample. With these assumptions, the populations are compared with the \(t\)-test, the F-test or the ANOVA test when suitable. Finally, a discussion of the results is presented. The results of the trials performed on both CS and DBS show a significant difference, as shown in Figure 6. The figure presents a boxplot with the overall success rate of the eight stimulation patterns under test. It takes into account the three recognition attempts for each pattern. Note that there is no median line inside the box because it coincides with both the 25 th percentile and the 75 th percentile for the CS and the DBS, respectively. Figure 6: Success rates of the performed tests on control subjects (CS) and deaf-blind subjects (DBS). The plot takes into account the three recognition attempts for each taction. A better performance by the DBS is noticeable. The boxplots display the success rate for 18 CS and 4 DBS. The performance was analysed by unpaired _t_-test, which shows different behaviour between the CS and the DBS (_p_ < 0.01). A large difference was observed in the mean success rates: 81% for CS and 97% for DBS. The _t_-test was applied to the two data sets assuming that have the same variance, as the result of the F-test showed that this assumption was reasonable (F(17,3) = 3.399, \(p\) = 0.171). After the comparative analysis between population samples, the extended trials performed on the DBS were analysed. Table 2 shows the raw scores achieved during these trials. Their tactile pattern recognition improved in the first attempt from 63% to 71% after the instruction. However, the overall average success rate over the three attempts remained at 97%, while the worst score improved from 87% to 90%, and the statistical mode was 100%. Thus, for the HMI practical purposes, the twenty possible patterns can be recognized with high effectiveness. Table 2 displays the four possible cases when guessing each stimulation pattern within the three attempts. Tactons are defined in Table 1. The influence of having either one or more active tactors at the same time is widely reflected in the pattern recognition performance. At first glance, this outcome can be extracted from the obtained data because the patterns applied to a single tactor indicate a success rate of 100%. In contrast, a lower efficiency is achieved with those patterns that activate more than one tactor. The paired _t_-test applied to these experimental data (one active tactor vs. multiple active tactors data) reinforces the previous impression (_p_ = 0.04). In fact, it was noticed that the patterns that simultaneously stimulate the middle finger and the ring finger confuse the subjects, so further analysis should be done. The two keying frequencies chosen--1 Hz and 10 Hz--were used either isolated or combined. As explained previously, the chosen values present great vibrotactile acuity on the skin. Moreover, the 170 Hz burst stimulus contributes to the performance because of the high vibrotactile sensitivity of the fingers at that frequency [42]. Thus, the results should be consistent with these statements. Therefore, the one-way ANOVA test (factor: frequencies) reflects no significant difference in recognition both for the isolated keying frequencies--1 Hz and 10 Hz--and their combination (_p_ = 0.730). The patterns listed in Table 1 are applied evenly to all five fingers of the right hand.