ABSTRACT
In this chapter, we move to the top right-hand cell of Table 7.1 and discuss methods based on models where the manifest variables are categorical. We start with the case where they are all binary — that is, where they are based on responses of the kind yes/no or right/wrong. Some methods appropriate when there are more than two categories will be given in Chapter 9. The word “trait” in the name of these models is often used because it arises from one of the principal applications for which they were devised, namely the measurement of psychological traits. In this book, they are used in a much broader context and so it seemed appropriate to make this clear in the title of the chapter. Nevertheless, we have also retained the original terminology to keep the link with a very important field of application.
