How do the advantages of a flipped classroom overcome timing issues?

First, I should note that the details of how people implement things that get called a "flipped classroom" seem to vary wildly, so my answers will be based on the version I've taught, and to a lesser extend the ones I seen my colleagues teach or heard them describe.

Having the students watch a lecture offline would mean they have to ask questions about that lecture without context and they would not have the answer to the question before watching the rest of the lecture. I would expect this to lead to lower understanding.

In my opinion, the inability to ask questions on the spot is indeed a drawback. But there are substantial benefits that mitigate this. Most importantly, many students don't ask questions in lectures when they should. One of the major reasons is that they can't produce questions fast enough to keep up with the lecture; by the time they realize they're confused and formulate a question, the topic has moved on. In that sense, for many students a video is no different from a live lecture in this respect.

And with a video, students can watch at their own pace, which can include pausing the video to formulate a question (and possibly even get it answered) before continuing, or rewatching the video after the question has been answered.

Overall, moving lectures out of face time is one of the main benefits of a flipped classroom: most lectures aren't all that interactive---few questions get asked, and only by a few students, so the value added by the interaction is low. It's not zero, so the goal of a flipped classroom had better be to replace the lectures with a more valuable use of that time.

Similarly, having the students work through the homework problems in the presence of the lecturer/tutor would substantially reduce the number and/or length and/or difficulty of the homework questions simply due to available time. A typical homework question set would take several hours to work through and usually have a couple of relatively simple questions that lead up to questions requiring deeper understanding. I would be concerned that running a flipped classroom would mean those deeper understanding questions would never be attempted and/or discussed.

Every flipped classroom version I've seen also has out of class homework. They have the simpler questions take place out of class, and have at least some of the deeper ones take place in class. Furthermore, most of them try to make the deeper questions more deep than the ones that would have been asked in the corresponding lecture class, or if not, they at least demand that students engage more with the deep questions.

Indeed, this point is one of the main goals of flipped classrooms: with the instructor (and possibly TAs present), it becomes reasonable to demand more (and different) things of students because there's help available on the spot.

In my lecture classes, for instance, I usually find that there's very poor engagement on the deeper homework questions. A non-trivial fraction of students skip them (since they're generally not that big a fraction of the homework grade), and a large number of students don't take them seriously---they either scribble nonsense for partial credit, or it's clear that they've worked in groups and essentially copied an answer they don't understand from the one person in the group who got it.

In a flipped classroom, there was much less of this: the students sat there and worked through the hard problems, thought about them, and struggled with them the way they needed to, because I was there to make sure they did.

This answer isn't really distinct from Henry's, but I thought a second view might be of interest.

I have been using what might be described as a flipped classroom for one of my modules recently. You might say it's 'not fully flipped', but at least it fits generally with the broader concept of 'active learning'.

One reason I did so was to get my students to practice reading the textbook. My class is currently small, but there isn't time to answer every question for every student, so they need to be able to learn from a mathematical text. The problem is that students are not automatically any good at reading these texts, which are rather different to most other forms of literature. So rather than giving the students a video to watch, I gave them a chapter of the textbook to read, with a short quiz intended to test whether they have correctly read the text.

My other primary reason was to change which part of the learning process takes place in 'lectures'. As I see it, understanding new concepts in maths takes several steps:

• find out the definition
• play with basic examples to understand the definition
• use the definition to prove simple things
• gain intuition, understand unusual examples, extremes and pathologies
• prove more complex things
• write out clear solutions

In my experience lectures tend to focus heavily on the first and third steps. I felt that the information-transfer of step 1 was not really the best use of lecture time - the content itself can be communicated in other ways (like the textbook), and students are often not ready to ask their questions on first sighting of the definition. Also, I'm reasonably convinced that my students generally need the second step. Because lectures typically build very quickly on definitions that have just been introduced, students will struggle to make sense of much of the lecture at the time. By moving the information-transfer out of lectures, I've gained time I can use to let students attempt practice calculations for themselves, and address the questions they are stuck on.

Of course there are also down-sides. It is harder to present as much information to the students this way, and I find it more time-consuming to prepare, because I have to think more about what the students will understand at a given point, rather than what I have already written on the board. Also, requiring prep means more work for the students (which is thought to be one big factor in why flipped teaching works well, and why students don't like it), so to compensate I've reduced the quantity of 'problem-sheet questions'.

You mention in comments being concerned about introverted students. My personal view is that uniformity is not particularly helpful. Any form of teaching is likely to benefit some students more than others, and different styles also work better for different teachers. That aside though, I'm not sure that this style is intrinsicly problematic for introverts. For example, they would have more time to formulate any questions before class rather than during a lecture, so they might feel more comfortable asking for the help they need.