"Part I is concerned with fundamental concepts and summarizes the significance testing controversy. Outlined in Chapter 1 is the rationale of statistics reform. The history of the controversy about significance testing in psychology and other disciplines is recounted in this chapter. Principles of sampling and estimation that underlie confidence intervals and statistical tests are reviewed in Chapter 2. The logic and illogic of significance testing is considered in Chapter 3, and misunderstandings about p values are elaborated in Chapter 4. The purpose of Chapters 3-4 is to help you to understand critical weaknesses of statistical tests. Part II comprises four chapters about effect size estimation in comparative studies, where at least two different groups or conditions are contrasted. In Chapter 5, the rationale of effect size estimation is outlined and basic effect sizes for continuous outcomes are introduced. The problem of evaluating substantive significance is also considered.