For these situations in which an empirically vetted scale does not exist or is not suitable, a custom scale may be created. This document presents a com
prehensive 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. The concept of scale reliability is described, with guidelines for computing, interpreting, and using results to inform potential
modifications to a custom scale. Next, a method for investigating the dimensionality of a scale, exploratory factor analysis, is described, along with a walkthrough of
software implementation and results. Finally, confirmatory factor anal
ysis, a technique for testing a priori hypotheses about dimensionality, is presented