Introduction to ITSA

Chapter 1 introduces Interrupted Time Series Analysis (ITSA) as a toolbox for researchers whose data consist of a long sequence of observations | say, N ≥15 observations | measured before and after a treatment or intervention. Sometimes the treatment or intervention is implemented by the researcher, other times it occurs naturally or by accident. The chapter also describes a family of impact types, characterized by their onset (abrupt or gradual) and duration (permanent or temporary); and the essential role of counterfactual controls in causal inference. The chapter concludes with an outline and summary of the book's subsequent chapters.