CONSTRUCTING VALIDITY - BASIC ISSUES IN OBJECTIVE SCALE DEVELOPMENT

A primary goal of scale development is to create a valid measure of an underlying construct. We discuss theoretical principles, practical is sues, and pragmatic decisions to help developers maximize the construc t validity of scales and subscales. First, it is essential to begin wi th a clear conceptualization of the target construct. Moreover, the co ntent of the initial item pool should be overinclusive and item wordin g needs careful attention. Next, the item pool should be tested, along with variables that assess closely related constructs, on a heterogen eous sample representing the entire range of the target population. Fi nally, in selecting scale items, the goal is unidimensionality rather than internal consistency; this means that virtually all interitem cor relations should be moderate in magnitude. Factor analysis can play a crucial role in ensuring the unidimensionality and discriminant validi ty of scales.