The Terra Nova and the WISC-IV
By Inderbir Kaur Sandhu, Ph.D
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!