Flawed IQ scoring system: Important difference in American, Canadian scoring systems

For her research, Dr. Harrison and her colleagues examined the differences between Canadian and American WAIS-IV scores from 861 postsecondary students from across Ontario. The research identified a trend where the individual's scores were consistently lower using the Canadian test scoring system. The WAIS-IV scores are used to make diagnostic decisions on the person's ability relative to their peer group.

"Looking at the normal distribution of scores, you'd expect that only about five per cent of the population should get an IQ score of 75 or less," says Dr. Harrison. "However, while this was true when we scored their tests using the American norms, our findings showed that 21 per cent of college and university students in our sample had an IQ score this low when Canadian norms were used for scoring."

The trend was the same across all IQ scores, with Canadian young adults in college or university consistently receiving a lower IQ score if the Canadian norms were used. There were fewer gifted students identified when Canadian norms were used, as well as more students who were said to be intellectually impaired.

When scoring the WAIS-IV, Canadian psychologists have the option to compare the obtained raw score with the normative data gathered in either Canada or the USA.

Dr. Harrison notes these findings have serious implications for educational and neuropsychological testing. "Research shows that you can go from being classified as average to intellectually impaired based only on whether American or Canadian norms are used to rank the obtained raw IQ score."