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Different Scores on Different Intelligence Tests

By Inderbir Kaur Sandhu, Ph.D

Q: My daughter had WISC VI GAI test done in March 2010 by her school and she scored 147, with very high verbal comprehension scores: similarities 16, vocabulary 18, and comprehension 19; for perceptual reasoning: block design 12, picture concepts 15 and matrix reasoning 18.

However, her school just administered WJ-COG for her last month in preparation for grade acceleration, and the result seems to contradict with WISC IV result. Her WJ-COG GIA score is 133, with her verbal comprehension and passage comprehension second to the lowest of her all COG test results around 115 (SS with 65% bound). And her numbers reversed and Incomplete words stand out to be the lowest of her COG test score -- around 107.

I asked the school psychologist about the differences of the test results, but she said it would be incorrect to compare the tests, because WISC VI GAI only test for two measures, and with WJ-COG she tested the entire battery.

I am very confused by the test scores, which is more accurate? How to explain that her strongest measure in WISC VI is the 2nd weakest in WJ-COG? Also what does Numbers reversed and Incomplete words measure, and what does the score tell us?

Please help ASAP, as we will have meeting with the schools to discuss about the acceleration next week, and I hope I will understand what those test results really meant.

Thanks very much for your help.

A: The psychologist is right - no two tests should be compared since the measure and capture different strengths. Furthermore, done during two different times may also provide some difference. However, I can understand your concern about the discrepancies between the two.

In terms of scoring, the scoring for both the test is similar in a full scale kind of way; not a brief version of the tests. They have a mean of 100 and a standard deviation of 15, so scores of 130 on each test represents the 98th percentile. However, while this appears to be comparable, what is tested is not necessarily so. The WJ-COG has a reputation for being more diagnostic in nature, and due to that, it has more areas that may not necessarily reflect “raw intelligence”. These scores in turn can influence with the scoring.

GAI (General Ability Index) is a combination of the Verbal Comprehension (VC) and Perceptual Reasoning (PR) subtests. It takes out the Working Memory and Processing Speed portions of the full scale IQ. So if there is a processing issue, it may pull down the FSIQ which is common in children who are gifted and at the same time have a learning disability.

The WISC-IV is a strong test for verbally gifted children, with emphasis on knowledge gained from reading. This version of the WISC, however, is also heavily timed. Short term memory and processing speed scales often lower the full scale IQ score for gifted children. The alternate scoring (GAI) is used in cases where the difference between the verbal scale and short term memory or processing speed scales exceed limits. Apparently, The WJ-COG, with its large variety of subtests, is said to provide the most information in the potential identification of twice exceptional (gifted and learning disabled) children.

Numbers reversed is tested by repeating increasingly long series of dictated digits in reversed order. This is a measure of short term memory. Incomplete words requires the examinee to attempt to recognize words dictated with some sounds omitted. It measures auditory analysis and auditory closure, aspects of phonemic awareness and phonetic coding.
You need to present the two test results to the school for their team to make a decision. Since the school uses WJ-COG for their acceleration program, the scores in the said test would determine if acceleration id suitable. Wishing you all the best.


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