In the last article on IQ scores, we talked about the origins of IQ testing, some definitions, and the statistical basis of IQ scores. Let’s continue with a discussion of what those scores mean.
Anytime your child is given a “standardized test” – including an IQ test – that test is meant to describe where your child stacks up on the bell curve when compared to other children his age. And your child really is being compared to other children his age. Standardized test scores come from giving the test to lots and lots of real children. The good, well-standardized tests (for example, the Wechsler Intelligence Scale for Children or the Stanford-Binet Intelligence Scales) are based on thousands and thousands of children, with the population of children matching the latest U.S. Census data for socio-economic status, racial diversity, urban/rural, etc. Another name for standardized tests is “norm-referenced tests”, because the scores are based on what is “normal” for a certain population of real people.
Standard scores are the number that describes where your child stacks up on the bell curve. IQ scores are standard scores. Percentile rank is another way of describing how a particular person ranks within a group. Percentile ranks should not be confused with percentages – they are very different, but very easily confused. If a child gets 60 percent on a test, that means she got 60 percent of the questions right and 40 percent of the questions wrong (not so good!). If a child is at the 60th percentile on a test, that means that she performed better than 60 percent of the children in the comparison group, and only 40 percent of the children in that group performed better than her (well-done!). Percentile ranks go with standard scores. A perfectly average standard score is 100, and that is at the 50th percentile.
On the Wechsler Intelligence Scale for Children (WISC) – the most widely used IQ test for children – IQ’s in the 70’s are considered “borderline” (slow learner), IQ’s in the 80’s are low average, IQ’s from 90-109 are average, IQ’s from 110-119 are high average, IQ’s in the 120’s are superior, and IQ’s 130 and above are very superior.
IQ tests are still used in schools today to help make decisions about eligibility for special education programs. The tests are given to children who are referred through the special education system. They are individually administered, scored, and interpreted by a school psychologist. The psychologist writes a report to explain the results, and this report is given to parents. In Transylvania County Schools, we have three excellent school psychologists on staff.
IQ tests are valid and reliable, but the scores are not written in stone. All kinds of things can lower a child’s score: illness, anxiety, language skills, fatigue, hunger, attention deficit disorder, behavior problems. The school psychologist gives parents a range (called a “confidence interval”) within which the “true score” should fall.
There are lots of different ways of being smart, and IQ tests measure just one of those ways: school smart, or book smart. IQ scores do not measure, for example, creativity, physical prowess, social intelligence, compassion, mechanical skills, spirituality, emotional intelligence, or intuition.
IQ tests do a great job of indicating who will have difficulty in school – which, after all, is what they were intended to do. They do not measure the value of a child and they do not predict success in life. IQ is just one way of looking at a person – an important way, but not the only way.