Generally speaking, Wang Shian may be slightly better than Changyu in probability theory, but only within the scope of postgraduate entrance examination, every teacher's level is enough to teach you, including Tang Shen and Yang Chao. Basically, there is no problem with the teaching quality of some famous teachers or even unknown teachers. The question is whose style you like, or who you can understand. Personally, I may prefer Zhang Yu. The classroom is more vivid and the content is easy to understand. Some people say that the number of questions is small. I don't think the whole set is too small. I don't know Wang very well, but he is also a teacher with good reputation in the industry, and he teaches probability theory, and his level is beyond doubt. Generally speaking, you can choose any one of these famous teachers, and you can learn well from whoever you listen to. You can choose whoever you like according to your personal style, which is basically the case in recent years.