Classification and Developmental Psychopathology
A basic assumption underlying the writing of this text is that, to be competent in the clinical assessment of children and adolescents, much more knowledge is required than being able to simply administer tests, this being the easier part. Many other crucial areas of expertise are necessary for appropriately selecting the tests to be administered and for interpreting them after administration. One such area of expertise was the focus of the previous chapter: an understanding of the science of measuring psychological constructs. However, a more basic level of knowledge is needed for using measurement theory appropriately. That is, one must have a thorough understanding of the nature of the phenomenon being measured before determining the best method for measuring it. In particular, the constructs of interest discussed in this chapter are the emotional and behavioral functioning of youth. The first hint at the importance of this basic understanding of psychological constructs was made in the previous chapter on psychometrics. It should have become clear that good psychometric properties are not absolutes. They depend on the nature and characteristics of the specific psychological construct being assessed. For example, childhood depression is frequently characterized by multiple episodes of depression interspersed with periods of normal mood (Kovacs, 2001). Therefore, high stability estimates over lengthy time periods should not be expected. In fact, if such stability occurs, then one is measuring something that is not an episodic depression.