The present authors presume that the objective of psychological measurement is the development of meaningful scientific scales. However, in most instances, behavioral science data are a considerable distance from providing such scales. Much behavioral data are binary, and we will follow the path of noting ways of examining the consistency of such data and deriving scores to summarize it provided that it displays a satisfactory degree of consistency. Such scores are referred to as "assumed scales" or just "scores." These scores are assumed to be ordinal variables, not some higher level such as interval or ratio scales or quasi-continuous variables. If our ideal of the scientific process holds, assumed scales are then to be used in further studies and the relationships they enter into are determined. These may be such as to allow the elevation of the score to interval status and scientific scales. This process is largely beyond the scope of this book.