Step 1 Interpret the Full Scale IQ

The initial step in comprehensive analyses of WAIS-III profile fluctuations involves systematic statistical treatment of the most global score, Full Scale IQ. Following this initial step, proceed in a stepwise fashion to examination of the other IQs, Indexes, and, finally, specific subtests. Because the Full Scale IQ is the most reliable score in the battery (mean split-half coefficient of .98), it is the logical starting point in Wechsler profile interpretation. This score should be assigned an intellectual category, using Wechsler's (1997, Table 2.3, p. 25) classification system. The purpose of the verbal label is to facilitate communication, not to pigeonhole the subject, and most terms in Wechsler's system (e.g., Superior for IQs of 120-129 or Low Average for IQs in the 80s) communicate quite well to the professional and layperson alike. However, the terms used for IQs in the 70-79 range can be unclear. This range is called Borderline by Wechsler, and IQs of 69 and below are considered Extremely Low (formerly called Mentally Retarded). The term Borderline is indecisive, and may be confused with the DSM-IV psychiatric label of the same name. Examiners who are accustomed to Wechsler's classification system may wish to use it with a slight amendment: substituting Well Below Average for Borderline. We recommend examining the qualitative description for the confidence interval, not just the IQ alone. For example, if a FS-IQ is 108 and the 90% confidence interval is 104 to 113, then the person is functioning in the Average to High Average Range. Using such descriptive categories that correspond to the person's range of functioning helps to avoid pigeonholing an examinee, and provides a more accurate description of his or her abilities.

Next, the FS-IQ should be converted to a percentile rank, using Wechsler's (1997, pp. 197-198) Table A.5, which includes percentile ranks for every IQ. Finally, surrounding the Full Scale IQ with a band of error is essential to ensure that the IQ is perceived as a range rather than a specific number. Table A.5 in the WAIS-III Administration and Scoring Manual (Wechsler, 1997) presents bands of errors for FS-IQ at two levels of confidence (90% and 95%).

The confidence intervals provided in the WAIS-III Administration and Scoring Manual were derived from a method that uses the standard error of estimation (Psychological Corporation, 1997). This method uses an estimated true score rather than the observed score, which results in an asymmetrical interval around the observed score. This asymmetry is more noticeable on scores at the extremes of the bell curve (e.g., the 90% confidence interval for a V-IQ of 50 is 47-56) than on scores closer to the normative mean (e.g., the 90% confidence interval for a V-IQ of 100 is 96-104). This asymmetry exists because the estimated true score is always closer to the mean of the scale than is the observed score. Thus, a correction for true-score regression toward the mean is obtained when the confidence interval is based on the estimated true score and the standard error of estimation is used. Regardless of how the confidence intervals are calculated, it is important to utilize them to communicate, even to the novice, that scores on intelligence tests have a certain amount of built-in error. The WAIS-III Interpretive Worksheet presented at the end of Chapter 12 summarizes this step as well as all the others that follow.

The Role of Full Scale IQ in Profile Interpretation

The careful statistical treatment and categorization of the Full Scale IQ as the first interpretive step does not mean that it is holy, or even the most important result of the evaluation. As the most global score, it becomes the baseline of the individual's performance, the midpoint that establishes the person's own average level of functioning. This overall score then becomes the fulcrum for allowing the examiner to determine areas of strength and weakness within the total profile. The IQs are normative scores that rank the indi vidual against a representative reference group and establish whether he or she is deficient or average or bright or superior in overall functioning. But the crux of profile interpretation is ipsative, the evaluation of strong and weak areas relative to the person's own midpoint. Ipsative and normative interpretations are one and the same only in those instances when the person's mean score equals the population mean.

FS-IQ is that midpoint and, as such, becomes the target for the astute clinician, a target at which to take careful aim in the search for both integrities and deficiencies within the cognitive and behavioral domains. The individual tested makes an unspoken plea to the examiner not to summarize his or her intelligence in a single, cold number; the goal of profile interpretation should be to respond to that plea by identifying hypothesized strengths and weaknesses that extend well beyond the limited information provided by the FS-IQ and that will conceivably lead to practical recommendations that help answer the referral questions.

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Responses

  • kaarina repo
    What does borderline in a WAIS mean?
    8 years ago
  • carl
    When not to interpret the full scale IQ?
    3 years ago
  • kristian biermann
    When not to interpret Full IQ score WAISIII?
    2 years ago
  • banazir
    When is the full scale iq not relaible?
    1 year ago

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