Validation of the Beck Depression Inventory－II with Rasch Analysis
Date Issued
2006
Date
2006
Author(s)
Lee, Kung-Hsien
DOI
en-US
Abstract
The Beck Depression Inventory-II (BDI-II) total score was one of the most frequently used indicators of depression severity in research and clinics. However, the justification of this use was not well validated. Specifically, there were at least 4 psychometric issues that needed to be investigated empirically, including (1) the unidimensionality which warranted the summation of the BDI-II scores; (2) the appropriateness of category scoring criteria in each item; (3) the distributions of the BDI-II items and their response categories along the continuum of depression severity; and (4) the transformation of ordinal raw BDI-II total scores into interval data, which were more informative and allowed arithmetic computation.
The Rasch model, known as a one-parameter logistic model of item response theory, is particularly useful in investigating the aforementioned issues simultaneously. The objectives of this study were to validate the BDI-II with Rasch analyses, including (1) to confirm the unidimensionality by means of examining Rasch model-data fitting, (2) to check the appropriateness of the category scoring criteria, (3) to inspect the distributions of items and their response categories along the continuum of depression severity, and (4) to transform ordinal raw BDI-II total scores into interval Rasch logits.
Data were derived from a study with 260 clients diagnosed with major depressive disorders (Steer et al., 2001). The model-data fitting was examined by fit statistics. To fulfill the assumptions of the Rasch model, the remaining analyses were performed with the fitted BDI-II items only.
All items fitted the Rasch model’s expectation, and thus the unidimensionality, except the item “Loss of Interest in Sex”. After removal of the misfit item, the remaining 20 BDI-II items all fitted the unidimensionality. Five items in which one or more response categories were less probable to be endorsed across various degrees of depression severity were identified, and thus the category scoring criteria may need to be revised in the future, including the items “Sadness”, “Punishment Feelings”, “Crying”, “Loss of Interest”, and “Changes in Appetite”. However, the resulting errors were within acceptable ranges, so they were kept at this stage. The 20 fitted BDI-II items and their response categories were found to be evenly distributed along the continuum of depression severity, and to cover, with this distribution, the depression severity of the clients with major depressive disorders in this study fairly well. The ordinal raw total scores of the 20 fitted BDI-II items were transformed into interval logits with the Rasch model.
Generally, the 20 fitted BDI-II items that constituted a unidimensional construct of depression would be able to discriminate different levels of depression severity and were suitable to measure the depression severity of the clients with major depressive disorders. Moreover, the Rasch transformed interval logits of the total scores of the 20 fitted BDI-II items were suggested for use by future clinicians and researchers because the transformed data can provide more information than ordinal raw BDI-II total scores and allow arithmetic computation and the application of more powerful parametric statistics without the threat of violating statistical assumptions.
Subjects
憂鬱
貝克憂鬱量表
心理計量
羅序模式
項目反應理論
depression
psychometrics
Rasch model
item response theory
Type
text
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