The third edition of Probability Theory and Mathematical Statistics has two versions, Wei Zongshu and Yan, but the content is basically the same. They all introduced the basic concepts, theorems and methods of probability theory and mathematical statistics and applied them to various fields.

The Course of Probability Theory and Mathematical Statistics published by Wei Zongshu is a difficult book. The basic concepts and methods of probability theory and mathematical statistics are introduced in detail, including random events, probability, random variables, distribution function, mathematical expectation, law of large numbers, central limit theorem, parameter estimation, hypothesis testing, variance analysis and regression analysis. This book is difficult and suitable for readers who have higher requirements on probability theory and mathematical statistics.

Yan's Course of Probability Theory and Mathematical Statistics is a book published by Higher Education Press in 20 19. The authors are Yan, Cheng and Pu Xiaolong. This book mainly introduces the basic concepts and methods of probability theory and mathematical statistics, including random events, probability, random variables, distribution functions, mathematical expectations, law of large numbers, central limit theorem, parameter estimation, hypothesis testing, variance analysis, regression analysis and so on. The book pays attention to application, explains the introduction and application of concepts well, and is suitable for beginners.

In short, the contents of the two books are basically the same, but the difficulty and emphasis are slightly different. Readers can choose their own version according to their own needs and level.