Extremely low
More than two standard deviations below the mean.
What this band represents
Scores below 70 fall more than two standard deviations beneath the population mean of 100. In clinical contexts, this band is one of several criteria used in the diagnosis of intellectual disability — but only one. The DSM-5 and ICD-11 both require evidence of impairment in adaptive functioning across conceptual, social, and practical domains, in addition to a low score on a standardized cognitive test administered by a qualified clinician. A single online screener cannot diagnose anything: at minimum, a clinical battery such as the WAIS-IV or Stanford-Binet 5 administered in person is required.
Important context
It is also worth remembering that any single test result carries measurement error. The standard error of measurement on the WAIS-IV is roughly ±5 IQ points, which means a measured score of 65 has a 95% confidence interval of about 55-75. People in this band can and do live independent, fulfilling lives, particularly with appropriate support and structure.
A note of caution. If you scored in this band on this screener and have concerns about cognitive functioning, please seek a formal evaluation rather than treating the result as diagnostic.
How this band sits in the population
- Score range: below 70
- Percentile range: Below 2nd percentile
- Population frequency: Roughly 2.3% of the population
- z-score range: z < -2.0
Frequently asked questions about this band
- What is a "good" IQ score?
- How accurate are online IQ tests?
- Can IQ be improved with practice?
- Why did I get different scores on different IQ tests?