The whole class is a straight reiteration of the textbook. The teaching approach in general is just not really teaching. After the midterm I completely lost what we were doing. I am still not sure I internalized anything fundamental about distributions. And that is unfortunate 'cause I really need to understand the material well for my future CS class. Be sure to check the weights of the exams. In our midterm (there's one midterm and final) each point corresponded to 1% of the final grade. And of course this class is not an exception to the mockery that is the math department during pandemic: exams are twice as long and at least twice as hard as they would have been in person. The people who do not cheat are punished the most, so...

Maybe I'm the stupid one in the class as everyone in the class gets like As on their tests. Not the best lecturer, but also not the worse. The test are extremely long and definitely not 3 hours for the finals. The class is not curved so keep that in mind (45% midterm, 25% hw, 35% finals). I just pnp the class cuz I know I will not learn anything from the class. Take it with another professor if you can.

The worst class I have ever taken at UCLA, watching any of the lectures after week 3 is a waste of time. You'd be better off spending that time rereading the textbook and watching khan academy videos. The professor is hard to understand and barely explains the main concepts we need to cover. Although he doesn't give a lot of work, this means there is almost no structure to help you learn the material.

Extrmely hard course, but I disagree that he hate his students. Prof.Nguyen allow my late submission of homework(and no point deduction) though his syllabus said no. And he reply email very quickly, almost in 30 mins to 1 hour, so you can feel free to ask any time. He also give a lot of hard practice and talk about that in class. If you attend every class, you will be expert of actuarial problem. His exam is tough, especially his Final exam(I spent totally 3 hours for 7 questions), a lot computation and you should remember dozens of formula( no cheatsheet in exam). So I advice you study this course as a 5 credits course.

If there was a burnbook for professors he would definitely get the fugliest sl-t review. He hates his students so he gives them the worst tests, of which 30% is nothing he ever mentioned or taught.

I don't know what the professor did to make people write positive reviews - most of the student in this class agreed that he is literally the worst professor in the math department. His lecture was extremely unclear, and sometimes when he forgot how to prove a theorem, he just told the class to figure out on our own, saying that it would appear on an exam. His exams weren't hard, but with his teaching, half of the class did not do well. Other reviews said that he was pretty helpful, which wasn't true at all, and he did not care about his students' learning at all. My TA and the workload were the only good things about this class, and all other aspects were just pure crap. Avoid taking this class with this professor at all cost, and if you have any doubts about what was said in this review, just ask others who took this class with him. I suspect that people who wrote the lengthy positive reviews either wanted to trick others into suffering through this class like they did, or the professor made them do it - his 170E reviews are much more accurate than the ones on this page.

GENERAL WARNING: Though not listed as a prerequisite, make sure to take Math 131A or equivalent before taking this course, as there are proofs that involve the limits of sequences and series as well as exchanging limits and unions/intersections, summation/integration, etc. I believe these rigorous aspects are a part of the course regardless of the instructor, so having knowledge of relevant topics is really necessary.
Another general comment: Stochastic processes are, based on my limited knowledge of math, a very deep subject. Having taken honors math upper divs and some grad courses (in applied math, though), I could feel that some aspects were deliberately left out in the textbook and/or lectures as they involve more advanced knowledge in e.g. real analysis (more precisely, measure theory as I would guess). That being said, the course contents are still pretty well presented in both the textbook and Dr. Nguyen's lectures.
Textbook: Written by Prof. Rick Durrett at Duke University and completely free (available on his personal website). A very well-structured book with more than enough examples, which is good for understanding, but at the same time, it is a good idea to take notes in class and/or make notes of the important results, as they tend to scatter all along the way in the textbook.
Grading: 25% HW + 5% Discussion Attendance + 25% Midterm + 45% Final. Towards the end of the quarter, another grading scheme was added: 25% HW + 5% Discussion Attendance + 10% Midterm + 60% Final. The syllabus says that the class is not curved in either way, but I speculate that we got curved up a bit.
Lecture: In person, but lectures were recorded, at first with Zoom installed in the classroom but the quality was very bad, so he switched to his phone after a week or two. The lectures are very clear and at a reasonable pace, though I find them a bit slow sometimes. He went through important proofs and examples step by step, which is very helpful. The only caveat is that one concept or two showed up in HWs that he did not cover in class, so once in a while you need to read the textbook on your own.
Homework: Combination of textbook problems and self-written ones. I think they are well picked/written, as they either serve as good practice of using formulas covered in class, or ask you to prove important results (with reasonable difficulty) that appear later in the course or on the exams. Some problems took plenty of time to think about, but it is very rewarding once you figured out the key point. There were nine sets of five problems in the first eight, but the last homework due on the final day of instructions had nine problems, which was actually a bit too many.
OH: Dr. Nguyen is very happy to answer questions and read your work on the HW and help you write better solutions/proofs during office hours.
Exams: 1 midterm + 1 final. Both exams were in person and a bit pressing on time, with the final more so. The distributions of scores turned out to be okay. Having a good understanding of the lectures and homework problems is essential, especially considering that there is not much time to be at a loss or fix mistakes.
Overall Dr. Nguyen is a very great instructor for this course. Due to its challenging nature, our lecture ended up having just short of 20 students, but Dr. Nguyen is very willing to help and I felt I learned a lot in his class.

Prof Nguyen isn't the best math professor I've had at UCLA, but he's definitely up there. When I took Math 178A with him, I felt like he knew the material well (although sometimes he forgets formulas) and explained it clearly. He wrote on the blackboard but he also posted lecture notes on BruinLearn. In lectures, he also handed out practice problems printed for us, sometimes with a list of formulas. He also responded to emails at lightning speed and is generally super helpful.

Homework was pretty tough but manageable (we didn't have a good TA). If you have the formulas all at the back of your hand, the midterm was quite easy and fair. The final was brutal, but Prof Nguyen curved our grades at the end. Since the math department has had trouble getting professors to teach lately, if you do end up with Prof Nguyen for this class, you should be fine as long as you do the homework and genuinely try to understand what's going on and unpack the symbols and notations.

This class isn't easy, but if you put in the work on the homeworks/lectures and go to his office hours, you can succeed.

Just don't expect to do well on his exams with only a surface level understanding of the material

Grade Composition: 45% Midterm + 25% HWK (Assigned weekly from Week 2 to Week 10; 9 in total) + 30% Final

The Professor was very willing to help during his Office Hours. He did give clues to challenging homework problems.

The distribution of easy, medium, and hard questions on the exams was around 50%, 30%, and 20%.

The only thing I disliked about this class might be that my TA could hardly speak English. I simply skipped discussions and hardly took advantage of any resources from her.

Fair Professor and pretty tough class for me, so definitely requiring some hard work.