## 5 Conclusions  
In this research, we investigated the reliability of statistical design of experiments (DOE) methodology in analyzing and modeling the performance of VANET routing protocols, by applying three DOE methods, mainly the full factorial method, the Plackett-Burman method and the Taguchi method. The analysis and interpretation of the results led to the following conclusions.  
Methods based on the design of experiments methodology offer powerful mathematical, graphical and statistical techniques that allow accurate retrieval of information with low costs. This conveniently responds to the particular case of VANET simulations often requiring higher processing and execution times.  
Both the Plackett-Burman and the Taguchi methods have the advantage of reducing the number of experiments by half in comparison with the full factorial method. Indeed, the effects of four factors (node density, number of connections, black hole and wormhole attacks) on four responses (throughput, packet loss ratio, average end-to-end delay and routing overhead) were simultaneously assessed using only 8 experiments in the case of the Plackett-Burman and Taguchi methods, while 16 experiments were performed for the full factorial method. Consequently, the Taguchi method might be considered a better alternative to the full factorial method when the number of involved factors is large. Additionally, it is important to note that the Taguchi method proposes powerful orthogonal arrays to design the experiments.  
The findings indicate that the three methods allow efficient estimates of the most influencing factors. However, the overall trends of the main effects from the Taguchi method are much closer to those of the full factorial method than those obtained from the Plackett-Burman method.  
The ANOVA analysis reveals that no noticeable differences are detected between the three methods regarding the factors that are statistically significant. The discrepancies are observed in the ranking of factors based on the percentage contributions. This is due to how the collected data are analyzed since the FFD and the PBM focus only on the measured values of the response, whereas the Taguchi method uses signal-to-noise ratios based on both the mean and the variance of the response.  
Regarding the accuracy of the mathematical models, the results of the adjusted R-squared and the fitting plots show that the Taguchi method gives the best descriptive and predictive power followed by the Plackett-Burman and full factorial methods.  
Finally, it is essential to mention that these conclusions are relatively valid to our case study, limited by the number of factors considered and the assigned levels. Thus, interested researchers can perform their scientific studies based on their specific conditions and potential limitations. The goal was to demonstrate the practicability of the implementation of some DOE approaches since their application to the performance assessment is less addressed in the literature. As far as we know, we believe that no such comparative study was presented before that applies different DOE methods together for the evaluation and the modeling of VANET routing protocol performance.