Error in the measurement of low intellectual ability:Implications for research

Aim
Recent work has shown that there is more error in the measurement of low IQ than has previously been acknowledged, notably: poor stability, a floor effect, the Flynn effect and large disparities between different tests.

Method
In order to assess the degree to which these errors impact on scientific studies all the papers in two leading journals on intellectual disability, the Journal of Applied Research on Intellectual Disability and the American Journal on Mental Retardation, for the year 2008, were read and use of intellectual assessments noted.

Results
It was found that the majority of the papers referred to the concept of intelligence. However, only a few papers acknowledged that there may be some additional error in its measurement or considered how these errors may affect the results of the study being reported on.

Conclusions
It is consider how these errors could affect scientific studies into intellectual disabilities by reducing correlations, making significant results less likely and making it possible for incorrect conclusions to be reached by assuming that the results of different IQ tests are equivalent.