Reconsidering the Psychometrics of the GRS-S: Evidence for Parsimony in Measurement

• Published in: Assessment for effective intervention Vol. 46; no. 1; pp. 55 - 66
• Main Authors: Petscher, Yaacov, Pfeiffer, Steven I.
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01-12-2020; SAGE Publications and Hammill Institute on Disabilities; SAGE PUBLICATIONS, INC
• Subjects: Academically Gifted; Accuracy; Achievement Tests; Children; Cutting Scores; Evaluation; Factor Analysis; Factor Structure; Factor structures; Gifted children; Intelligence Tests; Item Analysis; Item Response Theory; Measurement; Psychometrics; Quantitative psychology; Rating Scales; Reliability; Scaling; Screening Tests; Test Reliability; gifted rating scales; WISC; item response theory; gifted screening; measurement
• ISSN: 1534-5084; 1938-7458
• DOI: 10.1177/1534508418824743

The authors evaluated measurement-level, factor-level, item-level, and scale-level revisions to the Gifted Rating Scales–School Form (GRS-S). Measurement-level considerations tested the extent to which treating the Likert-type scale rating as categorical or continuous produced different fit across unidimensional, correlated trait, and bifactor latent factor structures. Item- and scale-level analyses demonstrated that the GRS-S could be reduced from a 72-item assessment on a 9-point rating scale down to a 30-item assessment on a 3-point rating scale. Reliability from the reduced assessment was high (ω > .95). Receiver operating characteristic (ROC) curve comparisons between the original and reduced versions of the GRS-S showed that diagnostic accuracy (i.e., area under the curve) of the scales was comparable when considering cut scores of 120, 125, and 130 on the WISC-IV Full Scale (Wechsler Intelligence Scale for Child–Fourth Edition) and verbal IQ and the WIAT-III (Wechsler Individual Achievement Test–Third Edition) composite score. The findings suggest that a brief form of the GRS-S can be used as a universal or selective screener for giftedness without sacrificing key psychometric considerations.