Three-way probability theory 1, mathematical statistics 2, random analysis 3, 1 and 3-biased theory, 2-biased application, 2-wide employment path. 1 more classical, more basic, 3 more modern, and needs a good theoretical foundation. But 3 has a deep application in modern economics and finance. If the major is combined with the application of finance, you can find a job in the securities industry and investment companies after graduation.