# An Agile Approach to Improve the Usability of a Physical Telechabilitation Platform
## 4 Results and Discussion
### Third Iteration  
The third iteration began in May 2018. In this iteration, 14 mock-ups were designed taking into consideration the feedback from the previous iteration. For the third iteration, three experts and 39 participants were invited. In the heuristic evaluation, there were a total of 92 heuristic violations in all the mock-ups. The questionnaire interface had only four usability problems of major and minor severity. The usability problems were decreasing in quantity and severity throughout the evaluation process, complying in this way with the proposed objective of improving the global usability of the ePHoRT platform.  
Figure 6: Comparative chart of the heuristic violations: first and second iterations.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Question** & **First Iteration** & **Second Iteration** \\  & **(of the Users)** & **(of the Users)** \\ \hline Is the control for the action visible? & 45\% & 100\% \\ Will the interface allow the user to produce the effect the action has? & 55\% & 67\% \\ Will users succeed in performing this action? & 73\% & 100\% \\ Will users notice that the correct action has been executed successfully? & 55\% & 67\% \\ \hline \hline \end{tabular}
\end{table}
Table 5: Level of difficulty in completing a task: first and second iterations.  
Figure 7 shows the frequency of heuristic violations per interface. According to the results obtained from the heuristic evaluation, the experts reported that eight interfaces (57.14%) did not achieve appropriate feedback from the users. Therefore, the platform incurred a clear violation of the HP1 heuristic. In addition, of these eight interfaces, the experts reported the HP10 heuristic violation at the UI-1, UI-2, and UI-4 interfaces. Finally, the experts considered that six interfaces (42.86%) were not flexible or efficient in their use.  
The questionnaire interface had been the subject of all the iterations. The questionnaire interface is the interface that had the most controls, in comparison with the login interface, which had the most usability problems despite having very few controls. When comparing the results of the evaluation of these two interfaces, the positive results of the iterative evaluation process can clearly be verified. Figure 8 shows the questionnaire and login interfaces.  
Figure 8: Mock-ups designed.  
Figure 7: Frequency of heuristic violations per interface (UI-1 to UI-14): third iteration.  
The evaluation was complemented with the NASA-TLX assessment, with the purpose of measuring by experimentation the cognitive workload of the users when using the ePHoRT platform. The three tasks proposed (Table 4) were performed by the users and the first results showed that task T1 (31.33/100) had the highest global workload weighted, followed by task T2 (30.67/100), and task T3 (22.17/100). The results presented a low cognitive workload for patients in the three proposed tasks. However, we must consider that the results are only a prediction of what we would expect when performing the same evaluation on the final interfaces with real patients. As shown in Figure 9, task T2 places the greater workload on the users. The dimensions with the highest workload are Effort and Temporal Demand. The results indicate that in tasks T1 and T2 users experienced the need for a greater mental effort to complete a task on time as a result of the lack of feedback at the interface level.