The DAS face sheet offers a good opportunity to record scores
as confidence bands rather than as single points. The small cross bars on the
vertical lines under the subtests and clusters make it easy to mark off precise
score ranges. For the cluster scores and GCA or Special Nonverbal Composite, the
confidence band is already provided when you look up the score, so all that is
needed is an X or heavy cross bar at the score, smaller cross bars at the ends
of the confidence interval, and a heavy, vertical line between the smaller cross
bars as shown in Figure 1.
Figure 1.
For individual subtests, the process requires an extra step
to compute the confidence interval. When you look up the Ability Score for the
student’s raw score, you find the Standard Error of Measurement (SE_{m})
or 68% confidence interval in parentheses to the right of the Ability Score.
Multiply the SE_{m }by 1.65 (1 2/3) for a 90% confidence interval or by
1.96 (2) for a 95% confidence band. In the example in Figure 2, a Raw
Score of 4 on Item Set 416 yields an Ability Score of 60 with an SE_{m }of
6. The 90% confidence band for an SE_{m }of 6 is 10 [1.65 x 6 = 9.90 »
10 or 1 2/3 x 6 = 6 12/3 = 10]. The 95% confidence band for the SE_{m }of
6 is 12 [1.96 x 6 = 11.76 » 12 or 2 x 6 = 12.]
Figure 2.
When you look up the T score for the Ability Score, also look
up the T score for the Ability Score minus the confidence interval and the T
score for the Ability Score plus the confidence interval. In our example, you
would look up the T Scores for 60 and for 60 ± 10 or
for 50, 60, and 70. You would make an X at 60, draw cross bars at 50 and 70, and
draw a heavy, vertical line between the cross bars. For the examiner’s
convenience, Table 9 shows 90% and 95% confidence intervals for SE_{m }values
from 1 through 20.
Table 9 90%
& 95% Confidence Intervals

Confidence Intervals 
SE_{m} 
90% 
95% 
1 
2 
2 
2 
3 
4 
3 
5 
6 
4 
7 
8 
5 
8 
10 
6 
10 
12 
7 
12 
14 
8 
13 
16 
9 
15 
18 
10 
17 
20 
11 
18 
22 
12 
20 
24 
13 
22 
26 
14 
23 
28 
15 
25 
30 
16 
27 
32 
17 
28 
34 
18 
30 
36 
19 
32 
38 
20 
33 
40 
A "psychograph" (Wechsler's term) with 90% or 95%
confidence bands encourages both examiner and reader to think of scores as
intervals, not as single points. The confidence bands reinforce the requirements
not to interpret insignificant differences between test scores and to be sure to
pay attention to significant differences between scores.