Why IQ Tests Are Bad Math

Some experts who study intelligence quotient (IQ) tests say these models are mathematically imperfect and can even lead to race and class discrimination.

- By Kat Friedrich

So how do IQ tests work, and what makes their methodology so shaky?

How We Measure IQ // "IQs are computed by percentiles. IQs tend to form a normal distribution. And so you compute how people compare to each other," explains Robert Sternberg, PhD, a professor of psychology at Cornell University. Most IQ tests have subscores, he says. These could be for verbal performance, math performance, or other skills. The total score is a weighted average of the subscores. On tests like the SAT and the ACT, the subscores are weighted equally.

"A lot of proprietary tests don't go into a lot of detail about their scoring because that's something they've copyrighted," says Elizabeth Dworak, PhD, a research assistant professor of medical social sciences at Northwestern University.