ABSTRACT
The focus in this chapter is on statistics and psychometric evidence that are involved in the process of using assessment data to make clinical decisions. As we emphasized in the first three chapters, a wide range of clinical decisions, from determining whether a client’s symptoms are consistent with the criteria associated with a diagnostic category and whether some form of intervention is indicated for the client, to determining whether an intervention should be terminated and whether a client has made meaningful gains in functioning, are all based on assessment data. Within psychometric theory, considerations about the implications and applied value of assessment data have been termed consequential validity (Messick, 1995). Both the ways in which test data and other assessment data are interpreted (e.g., the data indicate that a client’s distress is of a clinically significant magnitude) and judgments based on those data (e.g., the level of impairment in memory functioning indicates the need for special rehabilitation services) provide information pertinent to considerations of consequential validity.
