| Category | Descriptions | Supported citations |
---|---|---|---|
1. | Familiarity of flipped classroom | Some students held a conventional view of learning. | |
 |  | Some students did not get used to the routines of flipped classroom approach. | |
2. | Video lectures | Instructional videos were too long; and students could not focus on watching videos. | |
 |  | Watching videos were boring and passive. | Snyder et al. 2014 |
3. | In-class activities | Some students needed more clear instructions on how to work productivity in groups during class. | Grypp and Luebeck 2015 |
4. | Student workload | Pre-class activities were time consuming and overwhelmed students’ time at home. | |
5. | Out-of-class supports | Students could not ask questions immediately during video lectures. |