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The Terra Nova and the WISC-IVBy Inderbir Kaur Sandhu, Ph.D
Q: Can you tell me how accurate the InView portion (so-called IQ part) of the Terra Nova test is versus the WISC- IV?
How can I explain to a regular ed teacher that the Terra Nova IQ portion is not quite as accurate as an individual IQ test done by a licensed school psychologist?
A: I have discussed this in a previous query; however, I shall enhance the discussion here. Now, one needs to understand that "accuracy" is a rather strong word for such tests and may depend on various factors. The main difference between these tests is that the Terra Nova is an achievement test (nationally-standardized group assessment) whereas the WISC-IV (and others such as the Stanford-Binet) are ability/aptitude tests. This does not warrant a one-to-one comparison.
In principle, achievement tests are more directly concerned with what is taught is schools, which is not the case with ability tests. Most achievement tests items resemble closely to the knowledge and skills taught at school. As for ability tests, the skills tested may not be school based with less reliance to specific knowledge (e.g., analogical thinking, although essential for success, is not something that is taught at school). This is why students who score lower on an achievement test than on an ability test may be regarded as underachieving. However, this may not be true as there is no single test to measure potential in general and perhaps a combination of different tests may be better to determine the potential of a student.
Furthermore, on ability tests, there are clear cut tests of nonverbal skills which may not be as important or sometimes on-existent on achievement tests. Therefore, students who may have scored very high on nonverbal tests but much, lower on verbal and quantitative parts of an ability test may be perceptually oriented, but this may not be regarded highly in school as school-based subjects are mostly about symbols, that are numbers and letters. There is hardly any room for those who are perceptually oriented. Such a student may be seen as underachieving at school.
The Terra Nova tests compare students with others in their grades around the nation. Hence, the scores are listed in percentiles. It also includes a component that acts like an IQ test (the InView portion that you mentioned). This component measures the students' ability to use information and apply it to new and different situations. It also gauges how a student analyzes and employs higher-level thinking skills (includes verbal reasoning, sequences, analogies and quantitative reasoning). In short, it measures cognitive abilities that relate to a student's ability to learn and succeed in school. However, do bear in mind that this is a rather rough measure of intelligence.
In reality, these tests are just snapshots of a student's performance. Having said that, perhaps what you can explain to the regular ed teacher should be a along these lines. When the WISC is interpreted, a good psychologist would use professional judgment to determine if the Working Memory Index, Processing Speed Index, or both have significantly lowered the student's Full-Scale IQ score. Parents too always have the right to provide input for the evaluation of their child and their requests should be considered. This may be quite different from the Terra Nova interpretation.
Parent who can afford it more often than not seek private testing rather than testing at school. This is because a licensed school psychologist, for example may be evaluate and interpret scores and the child's needs more broadly. This enables them to consider a variety of educational possibilities which may be different from what the school may offer (limited possibilities offered by schools). Hence, the child's needs would be better catered for.
Hope the above provides some insights when you speak to the school teacher. Good luck!
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