A Bifactor and Item Response Theory Analysis of the Eating Disorder Inventory-3
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A Bifactor and Item Response Theory Analysis of the Eating Disorder Inventory-3 Jeffrey B. Brookings✉ 1
&
Dennis L. Jackson 2 & David M. Garner 3
# Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The Eating Disorder Inventory-3 (EDI-3; Garner, 2004) is a 91-item, self-report measure scored on 12 scales (three Eating Disorder Risk scales, nine Psychological scales) and six composites. A sample of 1206 female eating disorder patients was divided randomly into calibration (n = 607) and cross-validation (n = 599) samples for confirmatory factor analyses. A bifactor model best fit the data in both samples, but a model with second-order factors corresponding to the risk and psychological scales approached the fit of the bifactor model. Rasch analysis identified only two items whose level of misfit showed a lack of coherence with other scale items (the only items referring to drug and alcohol use), there were no items with reversed or “disordered” response categories, and only five items had sub-threshold estimated discrimination values. Overall, the results were supportive of the EDI-3’s psychometric properties and consistent with interpretive guidelines presented in the test manual. Keywords Eating disorders . EDI-3 . Confirmatory factor analysis . Rasch analysis
The Eating Disorder Inventory (EDI; Garner, Olmsted, & Polivy, 1983) was designed primarily as a clinical instrument that produces psychological profiles useful for case conceptualization and treatment planning for those with confirmed or suspected eating disorder diagnoses. However, the EDI has never been intended as a diagnostic instrument; within each diagnostic group, there is extraordinary variability on EDI psychological scales consistent with psychological traits that are theoretically unrelated or only weakly related to diagnostic markers such as behavioral symptoms and body weight. The measure has also been used as a research tool for assessing areas of psychopathology of interest in theory-testing,
* Jeffrey B. Brookings✉ [email protected] Dennis L. Jackson [email protected] David M. Garner [email protected] 1
Psychology Department, Wittenberg University, Springfield, OH 45504, USA
2
Department of Psychology , The University of Windsor , 401 Sunset Ave, N9B 3P4 Windsor, Canada
3
River Centre Foundation, 5019 Rolandale Ave, Toledo, OH 43623, USA
identifying meaningful patient subgroups, and assessing treatment outcome. Over time, the EDI has gained popularity among eating disorder clinicians and researchers and has been revised twice. The original EDI was comprised of 64 self-report items responded to on a six-point scale ranging from “Never” to “Always.” Item scores were then collapsed to a four-point scale (0–3) and the items assigned to eight scales which assessed individual differences in eating disorder risk (three scales) and associated psychological features (five scales). The “eating disorder risk” scales tap eating-disorder-specific symptoms and were later combined into a “composite” used to
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