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Differential Ability Scales (DAS)


Step-by-step Analysis

Step Six: Evaluate Shared Ability Hypotheses

  • Identify any relevant shared ability groupings

Elliott (1990, p. 100) in his description of the systematic interpretation of the DAS, provides what he called "Shared underlying processes" related to the DAS subtests. He has grouped together, and labeled as "shared abilities," sets of two or more subtests that appear to be assessing common capacities. The labels used for these sets of subtests are "suggestive" of the underlying processes. They are not meant to be definitive. They provide another avenue to pursue when generating hypotheses about a child performance. Shared ability groupings are based on the assumption that a child who performs poorly on a particular subtest will be weak in some, but probably not all, of the aspects of abilities measured by that subtest. Conversely, the child who performs very well on a subtest is not necessarily expected to perform well on all aspects of that subtest might assess.

To examine shared abilities examiners must first determine how each subtest compares to the student's overall mean for the test -- whether the subtest falls at, above (+), or below (-) the mean of the test. Subtests falling either above or below the mean are also examined to determine if they are falling statistically higher or lower than what would be expected. [We have chosen to use the terms High (H) or Low (L) rather than the more traditional Strength (S) or Weakness (W). We do this to make clear that all analysis is done relative to the child and to emphasize that a subtest that does in fact deviate from the mean of the test may be "below the child's mean" but still within the average range of scores. It is not appropriate to use the term "weakness" for a score that is average or higher by the test norms, nor the term "strength" for a score that is below the average range. Using the less value-laden terms of High and Low may prevent misinterpretation of the DAS results.] Figure-4 shows a portion of the DAS Analysis Sheet that represents the shared ability groupings. Examiners begin the evaluation of each shared ability grouping by entering either a + (higher), - (lower), H (significantly higher), or L (significantly lower) into the box below each subtest that differs from the student's own Mean Core T score. The box would be blank if the score were identical to the child's own Mean Core T score. These represent the relative standing for each of the DAS subtests when compared to the child's overall mean on the test (Mean Core T score). Examiners then assess each grouping, noting especially those that contain subtests that are considered High (H) or Low (L). By noting whether the subtests within the groupings are consistent - all above the mean or all below the mean - examiners can hypothesize possible strengths or weaknesses within the specific abilities. A shared ability with all subtests above the mean and additionally at least one subtest rated as H would be considered a "Probable strength," while one with subtests all rated as "above the mean" but without any subtest being rated as H would be considered a "Possible strength." In the example below, the Verbal Information Retrieval (long-term memory) shared ability would not be considered a potential strength or weakness because neither of the subtests given (WDef and Sim) was rated as H or L and additionally, one was above the mean (+) while the other was below the mean (-). The Knowledge of Quantitative Concepts shared ability would be hypothesized as a "probable weakness" since both of the subtests that make up the ability are rated as L.

Figure -4   Shared Ability groupings (completed example)

Verbal Information Retrieval (Long term memory):

WDef

Sim

NVoc

ENC

H / L or + / -

-

+

Knowledge of Quantitative Concepts:

SQR (b)

SIP

H / L or + / -

L

L

Short term memory (general):

RDes

RDig

RObj

RPic

H / L or + / -

H

L

+

Visual short-term memory:

RDes

RObj

RPic

H / L or + / -

H

+

WDef = Word Definitions, Sim = Similarities, NVoc = Naming Vocabulary, ENC = Early Number Concepts, SQR = Sequential & Quantitative Reasoning, RDes = Recall of Designs, RDig = Recall of Digits, RObj = Recall of Objects, SIP = Speed of Information Processing, RPic = Recognition of Pictures

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Step Seven