## 3 Materials and Methods
### Research Variables and Instrument  
In this study, the main explanatory variable considered is whether or not the country of origin of the participating professors belongs to CABEI. This is a dichotomous nominal variable. The secondary explanatory variable is the tenure, private or public, of the university where the professors teach. This is also a dichotomous variable.  
The following explained variables are also considered: (i) self-concept of the participants' digital competence in the use of VR technologies; (ii) assessment of the didactic aspects of VR; (iii) assessment of the usability of VR by professors and students; (iv) level of perceived disadvantages of VR use in higher education; (v) perceived future use for VR in the universities of the region; and (vi) assessment of the didactic and formative effectiveness of VR use. All the explained variables were measured on Likert-type scales from 1 to 5, where the lowest rating corresponds to value 1 and the highest to value 5.  
For measuring these explained variables, a validated questionnaire [32] oriented to university professors about the perception of the use of VR technologies in higher education was used (Appendix A). The questionnaire consists of 22 questions, each of which requests a rating of an aspect related to the didactic use of VR on a scale of 1 to 5, where 1 means a very low rating and 5 means a very high rating. The validation of the instrument refers to the construct, which consisted of an exploratory factor analysis that allowed the identification of six families of questions that explain the construct [32] (Table 1): (i) self-concept of participants' digital competence in using VR (questions 1 to 3); (ii) rating of technical aspects of VR, including realism, immersion, and three-dimensional design (questions 4 to 7); (iii) rating of usability aspects of VR, including user experience, employability of VR in lessons, and perceived possibility at the participant's university implementing VR technologies (questions 8 to 10); (iv) disadvantages of VR, including costs, space required, human and technical resources used, training required by technicians and professors, and technological obsolescence of equipment (questions 11 to 15); (v) assessment of the future projection of the use of VR in higher education, including both immersive and non-immersive VR (questions 16 and 17); and (vi) assessment of the didactic and formative aspects of VR, including student acceptance of VR, its impact on academic performance, induced student motivation, impact on the development of lessons, university capacity to implement VR technologies, and didactic employability (questions 18 to 22). This distribution of the questions into six families, which correspond to the explained variables of the present study, allows explaining 54.1% of the variance [32]. Likewise, the instrument was validated in terms of its internal consistency (notice that the Cronbach's alpha parameters of the different families mentioned vary between 0.70 and 0.84 [32]).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Variable** & **Questions** \\ \hline Digital competence & 1 to 3 \\ Technical aspects & 4 to 7 \\ Usability & 8 to 10 \\ Disadvantages & 11 to 15 \\ Future projection & 16 to 17 \\ Didactic aspects & 18 to 22 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Explained variables and questions of the instrument (Appendix A).