# YouTube Videos in the Virtual Flipped Classroom Model Using Brain Signals and Facial Expressions
## 2 Methodology
### Data Collection  
In this study, the students underwent two standardized tests to measure their grammatical competency, in addition to a learning styles test. Both the students and the teachers also completed an opinion survey at the end of the teaching-learning process. * **Standardized tests to measure grammar competency**: Both tests were designed with 45 multiple-choice questions with four answer options. They were applied through _Google Forms_ during 45 min synchronous sessions on the _Zoom_ platform, one prior to starting the course (diagnostic) and another on the last day (final). The students responded on their mobile phones and, through their computer's camera, the teacher monitored the application through the _Zoom_ session. The contents that were evaluated are shown in Table 4.
* **Learning styles test:** The test selected to measure learning styles was the _ILS Index of Learning Style in Spanish_, prepared by [PERSON] and [PERSON] [23] at North Carolina State University, United States. The test consists of 44 questions that assess the learning styles and classify them into four indicators: active/reflective, sensitive/intuitive, visual/verbal, and global/sequential. The students had five days to answer the test through its official page and report their specific results in a _Google Form_, where they also uploaded their PDF report sheet obtained from the test site as evidence. This process facilitated the classification of the learning style of each student (see Table 5). \begin{table}
\begin{tabular}{l c} \hline \hline
**Topics** & **Number of Questions** \\ \hline \hline Variable grammatical categories: nouns, articles, pronouns, & 4 \\ adjectives, and verbs & \\ Invariable grammatical categories: conjunctions, prepositions, & 4 \\ adverbs, and interjections & \\ Prefixes, lexemes, suffixes, and grammemes & 3 \\ Accentuation & 4 \\ Orthography & 4 \\ Homographs, homophones, paronyms, synonyms, & 3 \\ and antoyms & \\ The simple sentence and its types: enuncinative, interrogative, & \\ exclamatory, optional, imperative, exhortative, doubtful, & 4 \\ and possibility/probability & \\ Syntactic components of the simple sentence: subject & \\ (nucleus and modifiers), predicate (nucleus, direct object, & 4 \\ indirect and circumstantial complements) & \\ Compound sentences: coordinated (copulative, distributive, & 6 \\ disjunctive, and adversative) and juxtaposed & \\ Subordinate clauses: nouns, adjectives, and adverbials & \\ (mode, time, place, condition, consequence, endings, & 9 \\ comparison, and concession) & \\ \hline \end{tabular}
\end{table} 
Table 4: Contents of the standardized tests. * **Opinion survey for students**: The survey was emailed to students via _Google Forms_, and students were given three days to complete it. The questions asked are shown in Table 6.
* **Opinion survey for teachers**: The survey was emailed to students via _Google Forms_, and students were given three days to complete it. The questions asked are shown in Table 6.
* **Opinion survey for teachers**: The survey was emailed to the participating teachers through _Google Forms_. The questions asked are shown in Table 7.