## 3 Results
### Data Analysis Performed by the Studies  
It is important to highlight the ways the various studies measured the participants' performance, as improvements on these measures could be used to assess the success of their training system. In order to analyse the acquired data, which most commonly includes collision [27; 29; 33; 36; 37; 42; 47; 53], completion time [27; 28; 29; 32; 33; 34; 35; 36; 37; 38; 39; 41; 42; 44; 47; 53; 55], joystic events [28; 32; 34; 35; 37; 46; 47], and cybersickness [34; 36; 38; 39; 42; 46; 47; 53], the studies used statistical analysis, specifically most used the ANOVA test [27; 33; 34; 36; 42; 43; 50; 53; 54] which compares the means of different samples. [PERSON] et al. [24], similarly to us, found that data were collected quantitatively mainly for task completion time, number of collisions, number of joysticks movements, cybersickness, and the user's SoP. The most used test to determine cybersickness is the Simulator Sickness Questionnaire (SSQ) [58], which asks participants to assign a score (from 0 to 3) to 16 possible symptoms of simulator sickness. The measures acquired in the different studies are reported in Table 3, together with the purpose of the studies to justify why specific data was collected. The most popular type of acquired data is quantitative, which can be objectively analysed and interpreted, however, at times, qualitative data collection is needed for a better understanding of the participants' subjective experience of the VR application. In fact, some of the studies [30; 48; 50; 51] collected data in terms of interviews and focus groups for an in-depth understanding of the usability and feasibility of their developed system. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Study** & **Purpose** & & **Analysis** \\ \hline \multirow{6}{*}{[PERSON] et al. [42]} & \multirow{3}{*}{To determine if the VR simulator had any effect on learning the driving skills needed to safely operate a real PW.} & \multirow{3}{*}{Completion time and collision within a real environment before and after training. An ANOVA statistical analysis was conducted. An SSQ was also completed by the group wearing an HMD.} \\  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \hline \multirow{6}{*}{[PERSON] et al. [45]} & \multirow{3}{*}{To see if the important elements of the environment are perceived as well as if the users follow the predefined path or they choose an own path.} & \multirow{3}{*}{A session recording tool was used, which analysed virtual movements of the users and their path.} \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \hline \multirow{6}{*}{[PERSON] et al. [29]} & \multirow{3}{*}{Evaluation of effectiveness of the systems with the different controllers and improvement.} & \multirow{3}{*}{The participants completed the environment twice, and during the second time the data was collected.} \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Data analysis performed by the studies.