This chapter introduces key concepts of inferential statistics, building on prior skills in descriptive analysis and data visualization in R. Readers will learn the purpose of inferential statistics in drawing conclusions from sample data, the different types of validity including internal and external validity, and the role of measurement validity and reliability in research accuracy. The chapter also covers various forms of reliability and measurement validity, the concept of statistical significance, the interpretation of p-values in hypothesis testing, and the role of the null hypothesis in statistical inference. Mastery of these foundational concepts prepares readers to apply more sophisticated statistical tests to answer research questions confidently.