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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)
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Verbal Information Retrieval (Long term memory): |
WDef |
Sim |
NVoc |
ENC |
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H / L or + / - |
- |
+ |
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Knowledge of Quantitative Concepts: |
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SQR (b) |
SIP |
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H / L or + / - |
L |
L |
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Short term memory (general): |
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RDes |
RDig |
RObj |
RPic |
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H / L or + / - |
H |
L |
+ |
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Visual short-term memory: |
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RDes |
RObj |
RPic |
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H / L or + / - |
H |
+ |
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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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