Good Practice Made Easy
Demographics-Predicted IQ Calculator
This tool is based on published methods used to estimate an individual's full-scale IQ based purely on demographic characteristics. Individual cognitive abilities can vary significantly, including being significantly impacted by cultural and social factors. These methods are an aid to premorbid estimation only and should be combined with other 'hold' tests and clinical judgement in forming an opinion.
Crawford Method
How do I count years of education?
Enter the total number of years of (full time) formal education, starting from the first year of primary school (usually age 5). For example, completing school to 18 = 13 years, 3 years bachelor's degree = ~16 years, PhD (full time)= ~19 years.
What does social educational status mean?
This 5-point classification reflects socioeconomic strata used in the original Crawford model, based primarily on occupation. We have updated the descriptors to include more modern terms. Select the group that best aligns with the person’s main or longest-held occupation.
Helmes / Barona Methods
How do I code education level?
This scale was used in the original Barona and Helmes studies. Select the category that best represents the person's total formal education, not including pre-school or kindergarten, including high school and tertiary study.
What do the occupation levels mean?
These categories follow the original Barona and Helmes classifications and are based on demographic codes from the WAIS-R. Choose the occupational category that best represents your clients most usual (not necessarily current) work.
What is meant by rural or urban?
Helmes classified town/city of residence as 'urban' if the population was 2,500 or greater, and 'rural' if less than that. Use census data or local knowledge to estimate the typical population size of the area where the person lives or grew up.
What if someone is non-binary or transgender?
These models were developed using binary sex categories (female/male). This is a limitation of older models. If uncertain, use clinical judgment to select the category that most closely reflects the individual’s background.
Why is ethnicity included?
These estimates are based on Barona and Helmes' demographic samples, where ethnicity was a statistically significant variable in predicting IQ scores. However we acknowledge that estimates of IQ based on ethicity are highly problematic. Please use clinical judgement in applying these equations, alongside other indicators, choosing the option that most closely reflects the individual's cultural or ethnic background.
Why use a Flynn correction?
Calculations based on older versions of the WAIS often overestimate IQ scores, due to population-level changes over time (Flynn effect). These original models were all derived from the WAIS-R. This correction seeks to estimate equivalent WAIS-IV scores, using the method described by Kirton et al. (2020). For WAIS-R to WAIS-IV, this typically reduces the predicted IQ score by around 6 points.