Theory and Practice
Step 2 Step 2
ancies within the child.
Step 3. Compare subtest scores within each PASS Scale for meaningful discrepancies, if appropriate.
Step 4. Compare the child's Full Scale and PASS standard scores with achievement scores.
Step 1
Evaluate the child's overall levels of performance by describing the PASS and Full Scale standard scores using the descriptive categories, confidence inter- vals, and percentile ranks. This information should be recorded on the front of the CAS Record Form, as shown in Figure 2.2.
The Full Scale score is intended to be an overall estimate of processing based on the combination of the four PASS areas. That is, it is intended to be a convenient summary of performance. It will be a good overall description of a child's cognitive processing when the four PASS Scale scores are similar.
However, when there is significant variability among the PASS Scale standard scores, the Full Scale will not show important relative strengths and weak- nesses (as discussed in the section that follows). When this happens, the Full Scale score should be described as a midpoint between extreme scores and should be deemphasized.
Step 2
One of the main goals of the CAS is to examine differences in the four PASS Scale scores for an individual child, so that cognitive strengths or weak- nesses may be found. This is accomplished by examining the statistical significance of the variation in PASS scores, that is, interpreting the profile using an intraindividual (i.e., ipsative; see Kaufman, 1994) method. Such an approach gives the professional a way to determine when the variation in PASS scores is meaningful. When the variation is not significant, any differ- ences are assumed to reflect measurement error. Meaningful, or reliable, variation can be interpreted within the context of the theory, related to strat- egy use, and evaluated in relation to achievement tests.
When a PASS score is significantly above the child's mean score, a cogni- tive processing strength is found. When a PASS score is significantly lower than the child's mean score, a weakness is detected. Note that the strengths and weaknesses are determined relative to the child's own average level of performance. This approach has been used in intelligence testing (see Kauf- man, 1994; Naglieri, 1993; Sattler, 1988) for some time. The steps needed to determine if a child's PASS profile is significant are enumerated below.
1. Calculate the average of the four PASS standard scores.
2. Subtract the mean from each of the PASS standard scores to obtain the intraindividual difference scores.
3. Compare the intraindividual difference scores (ignore the sign) to the values in Table 4.3 presented by Naglieri (1999) or to the more detailed tables in the CAS Administration and Scoring Manual (Naglieri & Das, 1997c). When the difference score is equal to or greater than the tabled values, the score differs significantly from the child's average PASS Scale standard score.
4. Label any significant score that is above the mean as a strength, and those below the mean as a weakness. Any variation from the mean that is not significant should be considered chance fluctuation.
"The Case of Leslie," presented later in this chapter, uses the PASS scores presented in Table 2.2 to illustrate the interpretive process. The values needed for determination of significance for the Standard and Basic Batter- ies are provided by Naglieri (1999) and Naglieri and Das (1997b).
Illustration of the Method. The PASS scores provided in Table 2.2 vary from a low of 81 in Planning to a high of 98 in the Attention and Successive scales. The child's mean score for the four PASS scales is 91.5. When com- pared to this mean, and using the values needed for significance for the Stan- dard Battery, the Planning score is significantly lower than the child's mean.
This indicates that the child's Planning score is significantly weak relative to the overall level of performance.
Relative and Cognitive Strengths and Weaknesses. When there is a signifi- cant strength or weakness in the PASS Scale profile, the level of performance in relation to the standardization sample should also be considered. If a child has a significant intraindividual difference score that also falls below 90 (i.e., in the Low Average range or lower), then this difference should be labeled a cognitive weakness. This is true for the case of Leslie; her Planning scale stan~
TABLE 2.2 Leslie's CAS S c o r e s
Standard confidence Difference Difference 90%
score Percentile interval range from mean needed SIG/NS
Planning 81 10 76-91
Simultaneous 89 23 83- 96
Attention 98 45 91-106
Successive 98 45 92-105
PASS Mean 91.5
Full Scale 88 21 84-93
-10.5 9.7 SIG
-2.5 8.6 NS
6.5 9.9 NS
6.5 8.6 NS
Note. Differences needed are at the .05 level. SIG, statistically significant; NS, not statistically significant.
dard score is significantly lower than her mean PASS scores and it falls below the Average category. Alternatively, when a child has a statistically significant weakness that falls within the Average range (90-110), this should be viewed as a relative weakness, because it is low in relation to the child's mean but still in the average range of normative expectations. In such an instance, the find~
ing may be important for a variety of reasons. For example, it could explain uneven academic performance for a child who typically performs very well. A cognitive weakness is a more serious finding, because it represents poor per- formance relative to peers as well as in comparison to the child's own level.
Base Rates of Occurrence. The frequency of occurrence of intraindividual PASS scale differences can also be examined. This is determined through use of the actuarial tables provided in Appendix D of the CAS Administration and Scoring Manual (Naglieri & Das, 1997b). These tables list the frequency of oc- currence of all possible intraindividual difference scores in the standardiza- tion sample, and they can help determine how typical the PASS profile is. For example, using the data provided for Leslie (see Table 2.2), the difference of 10.5 found for the Planning Scale occurred in about 25% of the CAS stan- dardization sample. The importance of this finding is therefore augmented by the fact that a weakness of this size is uncommon among those included in the normative group.