# YouTube Videos in the Virtual Flipped Classroom Model Using Brain Signals and Facial Expressions
## 2 Methodology  
### The Participating Population and the Procedure  
The population participating in this research consisted of 80 second-year high school students at the PrepaTec CCM private school located in Mexico City. Their ages were between 16 and 17 years old; 51 were female and the other 29 were male. This population participated in a summer course lasting five weeks. The objective was to improve grammatical competency in Spanish. The course enrollment was free. The Department of Spanish and Literature sent an email to all sophomores to invite them to participate. Thus, they were invited to take a free course to reinforce their grammatical competency in their mother tongue during the summer. The condition was that they committed to attending the entire course from the beginning to the end. Due to the availability of teachers, i.e., only three, the number of students was limited to thirty for each teacher. In addition, they completed a Google Form for registration. Eighty students were accepted into the course. Participating students took a diagnostic test to assess their grammatical competency one week prior to the course and the _ILS Index of Learning Style_ test of learning styles [23]. Both instruments were applied through technological platforms. A synchronous virtual session was established for the grammar test. The learning styles test was answered asynchronously by students individually. To carry out a more personalized and differentiated instruction, we grouped the population into three levels according to the results obtained in the diagnostic grammar test: _basic_ (28 students, scores from 47 to 64), _intermediate_ (27 students, scores 67 to 73), and _advanced_ (25 students, scores 76 to 93). Each of the three teachers involved received the results of the learning styles test to classify their students and design learning activities according to the variables considered in the responses: active/reflective, sensitive/intuitive, visual/verbal, and global/sequential. The course contained over 25 virtual synchronous sessions through the _Zoom_ platform. This tool was selected by the studied educational institution for academic continuity during confinement. In the first session, called class 0, the students were given the corresponding training to work with the Flipped Classroom model in a virtual modality. In this session, the methodology of the course was presented, and the students were taught to responsibly work with the videos at home: prepare an appropriate space and time to avoid interruptions and improve concentration, pause, repeat, take notes, write down their questions, and perform the exercises if any were included in the video. At the end of class 0, the students received the link to the first _YouTube_ video through the course's _WhatsApp_ group. Thereafter, following each class, the students received the link to the new video that they had to watch that afternoon at home to prepare for the following day's class. The following 23 synchronous sessions of the course were designed as follows (Table 3), taking as reference the class format for the Flipped Classroom model proposed by [PERSON] and [PERSON] [7]:  
The videos used to teach the topics were previously designed by the Department of Spanish and Literature of the campus (see examples in Appendix A). A video was produced for each topic in the course's educational program. These materials were produced with video design and editing tools: _iMovie_, _Movie_ _Maker_, and _PowToon_. Subsequently, the videos were placed on the _YouTube_ platform. The videos had to have the following characteristics:  
* **Content**: focused solely on the assigned topic, including some reinforcement of prior knowledge, if possible, and with short exercises to reinforce learning. * **Duration**: long enough to present the content in a concrete and precise way to adolescent students (between 5 and 10 min, approximately). * **Image:** high quality, attractive, and stimulating, adding various colors, illustrations, and visual effects.