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Interval between Administrations of IQ Tests
By Inderbir Kaur Sandhu, Ph.D
Q: I administered an IQ assessment (WISC V) to a child in April of 2017. They disagreed with my assessment and chose to seek an independent evaluation. The independent evaluator administered the exact same assessment instruments 3 months later. The scores were higher on the independent evaluation. What are the recommended time between administrations due to practice effects?
A: It is not advisable to retest with the same test within about 18 months to 2 years due to the "practice effect", which can potentially inflate scores. However, if a different test was used (e.g., Stanford-Binet) or a different version (WISC-IV), it is possible for a child to be tested at any time. In any case, the school may request for IQ test results that are less than two years old. This could be a reason to consider retesting.
In this case, for the very same test, it is not a practice to retest in such a short period of time. Having said that, it is quite difficult to inflate the scores of any individually administered IQ test as the responses provided are the children's own and not for a selection of answers (as in MCQs).
Any score should be considered a minimum measure of potential. This means that the highest scores (say between two tests) achieved provide us with the best picture of a person's potential, regardless of whether it is an earlier or later test. The variation between results may be due to any one of a number of factors. If the same test was administered (as in this case), the degree of experience of the person or the rapport they developed with the child while administering the test may be reflected in the results. With a shorter interval, there could be some practice effect as well, though not significant. It could also depend on the child's condition on the day of testing.
In any case, unless there is a good reason – interval between two tests should be allowed to eliminate any practice effect. If the scores are significantly higher, then something is just not right. But if the scores are similar or only slightly inflated, this is quite possible based on the reasons mentioned. Hope you find the information helpful. Best wishes..
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