Preface

This monograph describes a method of measurement termed Discretized analog (Discan) which was developed over a period of six years during which time it has been employed in the psychological assessment and monitoring of a diverse group of patients seen by the second author in the Psychiatry Department of the General Hospital, St. John’s, Newfoundland. Discan methodology provides an alternative to the usual rating scales (Likert or analog) for the measurement of subjective variables such as symptoms, attitudes, cognitive variables, mood, pain, and levels of functioning along their underlying continua. Instead of requiring a single overall judgement as is the case with the conventional rating scales, Discan requires a small series of simpler component judgements. These component judgements, which are mostly dichotomous in nature, partition the underlying continuum into a substantial number of class-intervals, and allow us to define an optimal Discan in the sense of low measurement error. If it can be assumed that the process of scoring a Likert or an Analog scale involves implicitly a series of component judgements, then these scales can themselves be subsumed by the Discan system of measurement. This observation leads to an important interpretation of the optimal Discan, namely, that it is a compromise between the Likert Scale at one extreme and the Analog scale at the other. Discan easily accommodates to the measurement of experiential states which are unique to the individual for use in single case studies. As well, any Likert (or ordered categorical scale) with standard levels, such as symptom rating scales incorporating various levels of severity can easily be adapted to this methodology. The reader may wish to omit certain of the more technical sections on first reading. In order to get a general feel for this methodology, a suggested strategy would be to follow the sequence of sections entitled: Zntroduction, Rating scales, The Discan method, Illustrative examples, Summary and remarks. The summary section is an overview giving the key points of Discan methodology.