After reading all those "great" reviews for this professor, I thought its a good choice to take Math 170S as one of my elective class, but I can't describe how awful this class was. Imagine someone just reads you the lecture note pdf that is already uploaded, word by word in slow motion and leaving the questions unsolved, then having a quiz every other week which takes so much time with only 2hr limit time. (Btw if you f*ckup your midterm, quizzes will worth 50% of your grade so really be careful on quizzes). Finally both midterm and final was the worst and impossible to pass since the instructor will be grading it himself with absolutely no partials.
My advise: This class is far away from being easy and useful, so don't waste your time on taking Math 170S with LYU and try whole quarter to pass the class, either take someone else or ovoid probability and stats.

Like everyone else who reviewed it this quarter I was highly disappointed. I truly enjoyed 170E and I was excited to take 170S with a professor who had good reviews on bruinwalk and learn more. However, his lectures were slow and he just read off his notes, he didn't use the textbook but instead compiled his own lecture notes which were very difficult to follow. Although you could use the textbook alongside it, his questions are often completely different to those asked in the textbook so you can't even use that as practice and they are hard and confusing. The quizzes were graded kindly but the midterm wasn't and I doubt the final will be.

I agree with the other reviews that were written this quarter. This class was far from good. I heard this professor was "one of the best" in the department, but boy I don't agree. Maybe Lyu has just been going through some circumstance this quarter, so I don't want to sound too harsh. This review will be long but I want to make sure I cover everything you should know, and be as helpful as I can.

First of all, there are two grading schemes for this class:
1) 35% Quiz, 30% Midterm, 35% Final
2) 50% Quiz, 50% Final

There is only one midterm for this class, and also 5 quizzes, which happen every other week. The annoying thing about the quizzes is that they are long. There is a 120 minute timer for the quizzes after you open it, and yes, you will most likely be using up the entire time. Quizzes are 3 long questions, but I highly suggest you do all the exercises in his lecture notes, as it will save you a lot of time because he'll often test you on those exact same questions. His TA grades the quizzes and our TA graded pretty nicely. So even though I had some wrong answers, I still got a good grade on the quizzes. However, we had to wait about 2-3 weeks for a quiz to be graded.

The midterm was 5 long questions, and I found these questions to be harder than the quiz questions. I thought I did decent after taking the midterm, but the professor grades pretty harshly on it, so try to justify every step you do. The midterm average was 58.47/70, median 60/70, max 69/70 :), sd 6.72. I'm not too sure how the average was high, maybe I'm just dumb.

Now, the final was 7 questions, but 5/7 questions were tested on the same topic that we learned during week 9, and the other two questions were weeks 8 and 10 topics. So the final wasn't really cumulative. I spent the whole day working on the exam, so just be prepared for that.

The professor is severely disorganized, I am not kidding. I should've known from the first day of class that there were several red flags. His syllabus wasn't updated, so the Zoom Links were from Summer 2020. He didn't send us the correct Zoom Link until 10 minutes before class. And there were also some other incorrect information on the syllabus. For example, he says that he'll post a quiz at 1 pm PST, but then because of some circumstance, he posted it at 6 or 8 pm. This was annoying because he didn't send us any updates that he'll post it late. Also, he wrote on his syllabus that he would post the midterm at 9 am, but instead he posted it at 1 pm..

My biggest complaint for this class are the amount of typos on the quizzes, exams, and lecture notes. There was a huge typo on the midterm that I believe left the question unsolvable, so I spent a long time on that question. He emailed us about the typo at 11 pm, but I wished he would have just disregarded that question.

His lectures are not that great, and he goes extremely slow, so you'll able to watch his lectures at 2x speed. I don't think they're that helpful either, because he basically copies from his lecture notes and skips a bunch of steps. I found his lecture notes hard to read because of the lack of explanation for each step, and he expects us to explain these steps on the exams. I also get scared when he asks us a question during lecture and no one knows the answer to them. He gets mad when we don't know the answer.

His lecture notes that he uploads are horrible in my opinion. I would be left confused because of the typos on the notes. So just read it carefully, and watch for inconsistent notations, and wrong calculations. There are some exercises on the lecture notes and I highly suggest you do all of them, because the quizzes and exams will be mostly similar to them. It might also be helpful if you use the textbook as well, because he does take some exercises from the textbook. Just be aware the textbook does use different notations than his lecture notes and his lecture notes contains some material that you can't find in the textbook, so just only use the textbook as a reference. If you're curious how these notes look, it's online on his website.

Our TA seemed really nice but I think she stopped hosting discussions and office hours around week 5. I only went to discussion during week 0 and I didn't find it helpful. However, I really do appreciate her for grading the quizzes, because I've gotten scores that I don't think I deserve. To add to this, the difficulty of this class is influenced by the TA. If your TA is a nice grader like mine, then it's not too difficult to pass, but if you have a harsh grader, then you'll have to put in a bit more work.

The upshot: I would recommend you stay away from this class and this professor! I'm not sure how the 170S professors are, but you can also look into taking Stats 100B. But if you have to stay in this class, it'll be okay. It's not the end of the world at all. You might be frustrated at times, but I still think this class is definitely doable. You'll have to play close attention to every detail on your quizzes and exams since grading can be rough. I just think this class could've been a lot better and I'm not satisfied with how much I learned from this class.

Edit: He graded the final pretty fast (1 week). But he didn't post the exam statistics nor exam solutions. Also got some questions wrong but didn't receive any feedback so I don't know what I did wrong. That's great. Also my 87.9% turned out to be a B+. I'm not sure how much he curved this class but since the midterm average was high, I expect that a lot of students got As.

I took 170s with him also because of good Bruinwalk reviews. But damn was I wrong. He just reads off his lecture notes and work out examples that are already worked out way clearer in the notes. His tests are hard asf, took me at least 8 hours for this final; unreasonably and needlessly hard. Some stuff he never taught and just expects us to magically know it. If it was in his lecture notes, the fault would be mine. However, it's not in the notes. I am left scrambling all over my notes trying to find where in the f^&k did I learn this. Do not take this class with him. You're wasting your tuition and sanity.

The class was pretty good, but I definitely felt that there were some things on the homework/exams that we did NOT go over in class and are not in the textbook. Classic UCLA professor, expecting us to figure out stuff we've never learned before on tests.

Since many and I got As, so this class is still doable. However, tests are clearly hard since the professor expects us to know things we didn't quite learn from lectures.

I struggled, and honestly, wasn't happy with the amount of knowledge I learned. We don't have HWs for this class, so perhaps lack of daily practice is the reason why I don't feel I learned much.

Before you decide to take MATH 170S (with LYU), remember to take a deep breath, look at the shiny sun and the blue sky, and tell yourself It will be all fine.

Professor Lyu goes through the contents pretty slowly but his lectures are well-structured. The difficulty of his tests is reasonable but the length is insane - although he gave us 24 hours to submit the exam, I don't feel good about spending 6 hours on a single final. There are tons of typos on his lecture notes and problem sets, but if the student truly understands the material, this wouldn't be an issue. My feeling for this class is mixed, but I would recommend taking his class if you don't mind studying a bit on your own.

Professor Lyu explains the materials clearly. Also if you did bad on the midterm, the percentage of quiz grades would increase, which is good. We have 2 hrs to do each quiz and the time is enough except for quiz 2 in which a lot of calculations need to be done. Midterm and Final Exam are much harder than the quizzes but they are still doable if you understand all the materials.

I took 170E with Ozel and now I am taking 170S with Lyu. I know Ozel has great reviews and the materials of 170E are much easier than 170S. But to be honest, I feel like I understand the materials of 170S with Lyu much more than I do for 170E with Ozel!!! I am not saying that Ozel is a bad professor. Instead, he is one of the best in ucla math dept. But I do not know why I feel like I do much better and even started to like Probabilities a lot more when I take Lyu's class. Probably because he talks super slow and I am able to watch his videos at 1.5~2x speed and feel like it's a lot less content lolll

workload is manageable even during intense summer session (one hw each week). I have to say that his hw are a little hard but my TA has been really helpful too.

Recommend!

He's the best. Great class made better by his clear and engaging lectures. Lecture notes were really informative and the examples he uses are very applicable to real-life industrial/finance problems.