Outside of randomized experiments, association does not imply causation, and yet there is nothing defective about our knowledge that smoking causes lung cancer, a conclusion reached in the absence of randomized experimentation with humans. How is that possible? If observed associations do not identify causal effects in observational studies, how can a sequence of such associations become decisive?

Two or more associations may each be susceptible to unmeasured biases, yet not susceptible to the same biases. An observational study has two evidence factors if it provides two comparisons susceptible to different biases that may be combined as if from independent studies of different data by different investigators, despite using the same data twice. If the two factors concur, then they may exhibit greater insensitivity to unmeasured biases than either factor exhibits on its own.

Replication and Evidence Factors in Observational Studies includes four parts:

• A concise introduction to causal inference, making the book self-contained
• Practical examples of evidence factors from the health and social sciences with analyses in R
• The theory of evidence factors
• Study design with evidence factors

A companion R package evident is available from CRAN.

"Concepts and Applications": readable by most people who use statistical methods for empirical research on human beings - epidemiologists, medical researchers, social scientists."Theory": readable to people with a PhD in statistics. The goal is to make the subject accessible without specialized knowledge, something not possible in articles.

"This book is the first to discuss evidence factors and is a valuable contribution. Statisticians working on observational studies would find the book useful. Empirical researchers who conduct observational studies would find Chapters 1-6 useful. I would say the book serves more as a reference than a textbook although the book is as lucidly written as any good textbook?I would strongly recommend publication. The book will be of wide interest to causal inference practitioners." (Ted Westling, University of Massachusetts, Amherst) "This book will be of wide interest to causal inference practitioners." (Joel Greenhouse, Carnegie Mellon University) "This book not only brings much of the discussion around the topic of replicability in causal inference in one place, it does it in a way accessible to most. I would absolutely recommend this book for publication. (i) A big strength is that the book is conscious of the balance it needs to keep among motivating the concept, providing technical exposure and demonstrating the application of the method. (ii) This book is self-contained. (iii) The R codes in the footnotes and more references to specific R packages to implement the methods is a huge plus for the book. (iv) Of course, more on this topic exists that is not covered in the book. This book gives necessary references to papers for curious readers. There is a clear distinction of the focus of chapters through 6 and the latter chapters? While the earlier chapters consider Evidence Factors in Practice, the later chapters are about the Theory of Evidence Factors. This distinction is important to illustrate ideas. It is also nice that the book rounds up the discussion at the end in Chapter 13 with many practical tools?This book not only brings much of the discussion around the topic of replicability in causal inference in one place, it does it in a way accessible to most. I would absolutely recommend this book for publication." (Bikram Karmakar, University of Florida) "Paul Rosenbaum is a gifted expositor of complex statistical concepts and methods. His books on analyzing data from observational studies are not only a pleasure to read and to learn from but are scholarly and erudite in ways that are not typical of writings in statistics?The proposed manuscript is in the same style as Rosenbaum's earlier books and therefore promises to be popular as a reference for research workers or as a textbook for advanced undergraduate or graduate students, i.e., readers with sufficient statistical maturity. There is a lot of conceptual and technical machinery required to understand and use statistical methods for causal inference. In this book Rosenbaum is taking a step back. His goal is to explicate the informal steps that lead to a consensus about a causal relationship in practice and to provide formal methods for interrogating and weighing evidence from studies to help the scientific community reach consensus about causal relationships. This book will be a valuable addition to the causal inference literature." (Dylan Small, University of Pennsylvania)