The chapters in Part VII are more pure applications than the others in this volume. Chapter 23, Witkin et al. (1976), was a study of criminality in XYY and XXY men in Copenhagen, stimulated by proposals by John Mitchell, the U.S. Attorney General under President Richard Nixon, to identify such babies at birth and warn their parents of the potential antisocial tendencies; see the introductory section of this article for the underlying reasoning. This study matched XXY and XYY males to normal XY males on height, IQ, education, and parental socioeconomic status. The method used was simple stratified matching. Further model-based adjustments were also made. This article was a true committee effort, with the different authors of the different parts not always agreeing on what was important to say or how to say it. A careful reading is therefore more confusing and interesting than usual.

Chapter 24, Rubin (1991b), was the written version of a President's Invited Address to the Biometric Society, and reported some matched sample analyses that I was doing for Sandoz Pharmaceuticals. The issue concerned the effects of switching from a name-brand drug to a generic version after the original drug's patent expired. In particular, Sandoz had an antipsychotic drug for which it was investigating evidence that switching from the name-brand to a generic version was potentially harmful. Much of the article concerns how to formulate this causal inference problem correctly, especially how to deal with the post-intervention information.