ABSTRACT
In the examples considered in Chapters 4 and 5, the factor was qualitative in the sense that the different groups that constituted the factor differed from each other in quality and not just in quantity. For example, at the beginning of Chapter 4, we discussed a study that compared four treatments for hypertension: drug therapy, biofeedback, dietary modification, and a combination of these approaches. Although we could assign the numbers 1, 2, 3, and 4 to the four treatments, it is not at all clear which treatment should be assigned a 1, which a 2, and so forth. In other words, we cannot describe the treatments in terms of differences in magnitude of a single quantity. In this sense, we might say that the treatment levels form a nominal scale. We have simply formed four groups, which serve to classify participants.
