Vetting Custom Scales - Understanding Reliability, Validity, and Dimensionality
For situations in which an empirically vetted scale does not exist or is not suitable, a custom scale may be created. This document presents a comprehensive process for establishing the defensible use of a custom scale. At the highest level, this process encompasses (1) establishing validity of the scale, (2) establishing reliability of the scale, and (3) assessing dimensionality, whether intended or unintended, of the scale. First, the concept of validity is described, including how validity may be established using operators and subject matter experts....