You need the skills mentioned above which are usually taught in degrees like Mathematics, Computer Science, Physics, Economics, or Quantitative Psychology. A secondary subject in Social and Behavioral Sciences is desirable to gain a needed understanding of how to work in Social and Behavioral Sciences empirically and of latent variables.
Applicants need to be familiar with topics like one- and multidimensional calculus, Linear Algebra, Statistics / Probability Theory, and need to have basic knowledge in algorithms and data structure (e.g., R or Python).