# Coloured Petri Nets-Based Modeling and Validation of Insulin Infusion Pump Systems
## 6 Empirical Evaluation
### Analysis  
Figure 10 depicts the answers for effort and each reusability factor evaluated in experiments 01 and 02, respectively. We did not apply more complex hypotheses tests such as the t-test and Wilcoxon test because the hypotheses were defined to evaluate RQI and RQI only use the mean responses concerning the factors considered in this experiment. The basic descriptive statistics enabled the evaluation of the hypotheses. For RQI, we evaluated the reference model's re-use based on the analysis of the improvement of the productivity of the modelers. The 12 modelers who participated in the experiment concluded instantiating the model, and in the average case, within six minutes.  
When asked to respond to the questionnaire, 66.7% of the modelers (8 of the 12 modelers) stated that the task of instantiating the reference model presented no effort. In contrast, 8.3% stated low effort, 16.7% stated medium effort, and 8.3% stated considerable effort. Thus, the hypotheses H0-1-1 and H0-1-2 were refuted, showing that the model presented a positive response to the RQI (the modelers used only 10% of the estimated time).  
We evaluated the reference model's re-use to analyze the RQI based on the understandability and adaptability factors. Figure 11 presents the number of modelers stating to extend the model considering the requirements 01 and/or 02, also including the number of modelers who experimented 02 correctly. All the modelers implemented requirement 01 (i.e., adding a new battery).  
However, only five of them implemented it successfully. The analyses of the work conducted by the seven modelers who did not implement the requirement 01 successfully showed that all of them failed in the same task: the marking of the Ok_B place (Verify Battery submodule) was not changed from 2'1 to 3'1. Six modelers attempted to implement requirement 02. However, only two of them achieved the correct answer. The results of the four modelers who did not achieve the correct implementation showed different mistakes, all related to the usage of CPN/ML.  
To analyze the time spent to conduct the second experiment, we considered the group related to each modeler. Figure 12 shows the time collected for the control and treatment group. Only one of the modelers successfully implemented the reference model's first and second requirements within 25 and 38 min, respectively. The modelers scaled the first requirement as a low-complexity task while disagreeing when asked about the complexity of the second requirement: the control group's modeler scaled as a medium-complex task. In contrast, the modeler of the treatment group scaled it as a low-complex task.  
Analyzing understandability and adaptability from the results presented in Figures 11 and 12 does not enable us to conclude that the reference model is fully reusable, requiring the analysis of results presented in Figure 10. Most modelers did not fully understand each component of the reference model's roles and functioning. The high number of modules required by the complexity of insulin infusion pump systems negatively impacted adapting the model adding new requirements.  
Figure 13 supports this claim showing modelers' answers for the complexity of each requirement added to the reference model in the second experiment. Most of the modelers stated the requirements 01 being of low (75%) or medium (25%) complexity, while stated medium or high complexity (75%) for requirement 02.  
Figure 11: Instantiated model vs. correctly instantiated.  
Figure 10: Answers distribution in accordance with the effort and reusability factors.  
The evaluation of R@2 based on the questioning presented to the modelers showed that HO-2-1 was refuted due to the mean classification of the understandability factor (approximately 3.17). For HO-2-2, the mean classification of the adaptability factor presented approximately 3.58, refuting the null hypothesis. Thus, the reference model presented acceptable levels of understandability and adaptability.