 
Differential Ability Scales
(DAS)
Stepbystep
Analysis
An Illustrative Case with the DAS
Kate, a 14 year old, was referred for evaluation because of difficulty in her
8^{th} grade classes, specifically in the areas related to mathematical
concepts and reasoning. Teachers had noted on the Learning Disabilities
Diagnostic Inventory (LDDI, 1999) that she frequently "Makes borrowing
errors," "Reaches 'unreasonable' answers," and "Has
difficulty in multistep problems."
Kate was administered the DAS and obtained the results in T scores, Standard
Scores, and Percentile Ranks for her age found
in Table  26.
Table 
Table  26
KATE’S DAS
SCORES AS T SCORES, STANDARD SCORES, AND PERCENTILE RANK FOR HER AGE

Total Scores
[letters in ( ) show subtests from below included in each Composite] 
Standard Score 
Percentile Rank 
Classification 
95% Confidence^{1} 
General Conceptual Ability
(WDef Sim Mat SQR RDes PCon) 
100 
50 
Average 
91109 
Verbal
(WDef Sim) 
103 
58 
Average 
93113 
Nonverbal Reasoning
(Mat SQR) 
78 
07 
Low 
7088 
Spatial
(RDes PCon) 
116 
86 
Above Average 
107124 

T Score 
Percentile Rank 
Classification 

Verbal Tests 




Words Definitions
(WDef) 
49 
46 
Average 

Similarities (Sim) 
56 
73 
Average 

Nonverbal Tests 




Matrices (Mat) 
43 
24 
Average 

Sequential & Quantitative Reasoning (SQR) 
32 
04 
Low 

Spatial Tests 




Recall of Designs (RDes) 
60 
84 
High 

Pattern Construction
(PCon) 
60 
84 
High 

Diagnostic Tests 




Recall of Digits (RDig) 
30 
02 
Low 

Recall of Objects  Immediate (ROi) 
55 
69 
Average 

Recall of Objects  Delayed (ROd) 
61 
86 
Above Average 

Speed of Information Processing (SIP) 
35 
07 
Low 

 Even the best tests are not perfectly consistent. Lucky and
unlucky guesses or barely beating or missing time limits, for
example, will cause scores to vary. The 95% confidence band shows
how much scores are likely to vary 95% of the time by pure chance.
WDef = Word Definitions, Sim = Similarities, Mat = Matrices, SQR =
Sequential & Quantitative Reasoning, RDes = Recall of Designs,
PCon = Pattern Construction, RDig = Recall of Digits, ROi = Recall of
ObjectsImmediate, ROd = Recall of ObjectsDelayed, SIP = Speed of
Information Processing 
The first step in interpreting Kate's results is an examination strictly from
a descriptive point of view  at what level of cognitive ability what did she
perform? Analysis at this stage is considered descriptive in nature since no
statistical comparisons have yet been made. Kate appears to be functioning
overall in the Average range, with a GCA score of 100 (94106, 59^{th}
percentile, Average). The GCA score comprises her other composite scores, and
these scores range from the low Nonverbal Reasoning score of 78 (7088, 10^{th}
percentile, Low) to her high Spatial score of 116 (107124, 81^{st}
percentile, High). Because of the differences between the scores, a careful
analysis of Kate's profile is warranted. Blindly accepting the perfectly Average
GCA score would neglect to take into consideration the seemingly diverse nature
of Kate's abilities.
Examining the subtest T scores also gives some preliminary description about
how Kate performed. Her core subtests ranged from a low of 32 (10^{th}
percentile) on the Sequential & Quantitative Reasoning subtest to a high of
60 (84^{th} percentile) on the two Spatial subtests, Recall of Designs
and Pattern Construction. The scores on the diagnostic subtests given to Kate
also reveal information from which to generate hypotheses. She did poorly on
both the Recall of Digits (2^{nd} percentile) and Speed of Information
Processing (7^{th} percentile) and yet performed average or above on
both the Recall of Objects  Immediate (69^{th} percentile) and 
Delayed (86^{th} percentile) subtests. Since Recall of Digits and Recall
of Objects both involve some aspect of memory, this area will need to be further
explored throughout the interpretation.
To continue the analysis of Kate's scores, examiners should complete each of
the steps outlined in the previous section of this chapter. Completing these
steps allows the hypothesis generation and resulting interpretation to be
integrated with all findings instead of continually generating hypotheses in one
step that might be quickly negated by the next step. For our example, the DAS
Analysis Sheet (Exhibit4) was
completed.
