# MobiDabet: Mobile Telemonitoring System for Patients with Type 2 Diabetes Mellitus (T2 DM)
## 4 Preliminary Usability Assessment of the Proposed System
### Preliminary Usability Assessment Results
#### 4.3.1 Results of the Preliminary Usability Assessment of the System Based on a Field Study  
**Results of instrument 1. **  
This instrument was applied to 2 nutritionists, 4 physicians, and 7 patients. The results were obtained by applying the following equations defined in the ISO/IEC 25,022 standard [16]. System effectiveness per user:  
\[x_{i}=A/B \tag{1}\]  
where, \(x_{i}\) is the effectiveness value of each user, \(A\) is the number of tasks completed, and \(B\) is the number of tasks attempted. The expression \(x_{i}\approx 1\) means that the user was able to reach the goals by completing all system tasks. To obtain the average effectiveness percentage (_effectiveness\({}_{avg}\)_), the effectiveness values of each user were added and divided by the total number of users:  
\[\textit{effectiveness}_{avg}=(\Sigma\ x_{i}N)\ 100 \tag{2}\]  
On the other hand, the system efficiency per user is calculated as follows:  
\[x_{i}=\Sigma\ x_{i}N \tag{3}\]  
where \(x_{i}\) is the average time of each user, \(x_{i}\) is the time to perform a task, and \(N\) means the total number of tasks. While \(x_{i}\) is closer to the planned time, it indicates that the user was able to reach the goals by completing all the tasks of the system in a satisfactory time. Then, the average time of tasks was calculated by:  
\[B=\Sigma\ x_{i}N \tag{4}\]  
where \(B\) is the average time of tasks, and \(N\) the total number of users. Finally, to obtain the average efficiency percentage, the following formula was applied:  
\[\textit{efficiency}_{avg}=(A/B)\ 100 \tag{5}\]  
where A means the estimated time of tasks and B the average time of tasks. The results obtained from the Instrument 1 show the percentage of effectiveness and efficiency of the system concerning whether users can complete the tasks of the system and the spent time (see Table 4). The results indicate that those physician users were able to complete the tasks of the system, reaching the desired goals with an average effectiveness of 95.8%. On the other hand, the efficiency of medical users in completing the system tasks obtained a result of 90.1%. Concerning nutritionist users, the results indicate that they were able to complete the tasks of the system, reaching the desired goals with an effectiveness of 94.1%. On the other hand, the efficiency of the nutritionist users in completing the system tasks obtained a result of 83%. Finally, the results indicate that patient users were able to complete the tasks of the system, reaching the desired goals with an effectiveness of 92.9%, and the \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type of User** & **Average Effectiveness Percentage** &
\begin{tabular}{c} **Average** \\ **Efficiency Percentage** \\ \end{tabular} \\ \hline Physicians & 95.8\% & 90.1\% \\ Nutritionist & 94.1\% & 83.0\% \\ Patients & 92.4\% & 63.4\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of efficacy and efficiency based on the analysis of the Instrument 1.  
efficiency of patient users in completing the tasks of the system obtained a result of 63.4%. According to the measurement scale proposed previously [19]:  
\[ \begin{array}{l}0\leq\%\ \text{effectiveness/efficiency}\leq 45:\\ 46\leq\%\ \text{effectiveness/efficiency}\leq 80:\\ 81\leq\%\ \text{effectiveness/efficiency}\leq 100:\\ \end{array}\begin{array}{l}\text{Not satisfactory}\\ \text{Acceptable}\\ \text{Satisfactory}\end{array} \]  
The web application aimed at the health personnel, in general, has a satisfactory level of effectiveness and efficiency from the point of view of physician and nutritionist users. On the other hand, the web application focused on the patient has a satisfactory level of efficacy and an acceptable level of efficiency. **Results of Instrument 2. **  
The results of Instrument 2 show the level of satisfaction of the system users. In this study, the user interface satisfaction questionnaire [17] was applied from the perspective of the three user profiles that used the applications that make up the system.