The Psychometric Anatomy of Two Unidimensional Workload Scales
AIR FORCE FLIGHT TEST CENTER EDWARDS AFB CA
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The intent of this paper is to encourage reevaluation of the unidimensional workload scaling used in aerospace test and evaluation applications. The more specific intent is to encourage reevaluation from a structured psychometric viewpoint. The end goal is to facilitate a uniformly higher standard of measurement quality in unidimensional scaling having complex scale step descriptors. The basic principles and methods of psychometrics have been accessible in the technical literatures for decades. Even so, they have not been consistently applied to the design and verification of scaling for aerospace crew station usability evaluations. Psychometric verification should be performed on every scale employed as a test and evaluation tool. To this end, a simple but powerful psychometric method is demonstrated via two case studies performed at the United States Air Force Flight Test Center AFFTC, Edwards Air Force Base California. Study 1 assessed the AFFTC revised United States Air Force School of Aerospace Medicine USAFSAM workload scale, while Study 2 assessed the Bedford workload scale. As was the case with the original USAFSAM, the Bedford was found to be psychometrically deficient, although the revised USAFSAM was verified to be psychometrically satisfactory.