| Abstract: | Thurstone's scaling based on judgments of 527 students and 37 clinical faculty members was applied to the Beck Depression Inventory, the Zung Depression Scale, and the MMPI-D30 and had a good fit to the observed data. A 4-unit unidimensional psychological continuum for depressive severity (Subjective Depression Severity Continuum [SDSC]) ranging from positive affect to severe depression was derived. Scale values (SVs) for each item's response options estimate their location on the SDSC and were shown to be face valid, stable, and unbiased by gender, race, depression level, or clinical training. Results showed that the original scoring procedures were not internally valid because they were not interval in level of measurement. As severity of content increased, perceived differences between response options decreased. 11 items had nonmonotonic response patterns. The magnitude of perceived severity was not constant for levels of severity (mild, moderate) or across symptoms (sadness, crying). The SVs represent an improvement over standard weights because they are interval in measurement, internally and face valid, and they allow one to equate the 3 scales or omit items. (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
