In this second edition of the book, two new chapters of great academic importance have been added, namely Chapter 14 on Multiple and Partial Correlation Regression, and Chapter 15 on Non-Parametric Methods. These chapters provide fundamental definitions and numerical examples on multiple and partial correlation coefficients, as well as Spearmans rank correlation, partial correlation, and multiple regression using appropriate statistical formulas. Additionally, Chapter 15 covers the most appropriate methods for analyzing data collected in social sciences, which is often based on answers provided by respondents through their memories and may suffer from memory lapses or intentional errors. The examples provided in both chapters will be valuable assets for readers and users to gain a fundamental understanding of the subject matter.