Below are the introductory paragraphs to IAP AP Brief #5. The complete report is available for online viewing or downloading by clicking here. Enjoy.
The ss 1-19 scale has a long history in the Wechsler batteries. For sample, in Appendix 1 of Measurement of Adult Intelligence (Wechsler, 1944), Wechsler described the steps used to translate subtest raw scores to the new ss metric. The Wechsler batteries have continued this tradition in each new revision, although the methodology and procedures to calculate the ss 1-19 values have become more sophisticated over time. Although the methods used to develop the Wechsler ss 1-19 scale may have become more sophisticated, the resultant underlying scale for each subtest has not…scores still range from 1-19 (M=10; SD=3). Also, the most recent Stanford-Binet—5th Edition (SB5; Roid, 2003) and Kaufman Assessment Battery for Children-2nd Edition (KABC-II) have both adopted the same ss 1-19 scale for their respective individual subtests.
Why is this relatively crude (to be defined below) scale metric still used in some intelligence batteries when other contemporary intelligence batteries provide subtest scale metrics with finer measurement resolution? For example, the DAS-II (Elliott, 2007) places individual test scores on the T-scale (M=50; SD=10), with scores that range from 10-90. The WJ III (McGrew & Woodcock, 2001) places all test and composite scores on the standard score (SS) metric associated with full scale and composite scores (M=100; SD=15). The critical question to be asked is “are there advantages or disadvantages to retaining the historical ss 1-19 scale or, are their real advantages to having individual test scales with finer measurement resolution (DAS-II; WJ III)?”
(complete report available at links in first paragraph of this post)
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