The current Stanford-Binet test (and the next one, which is in preparation) use the typical 15 points per standard deviation scoring. The Cattell test is not a

The current Stanford-Binet test (and the next one, which is in preparation) use the typical 15 points per standard deviation scoring. The Cattell test is not a "mainstream" IQ test and correlates rather poorly with expected variables that ought to correlate well with IQ like academic achievement. Standard scores by the current definition are readily converted to percentile ranks by look-up tables, by the definition of standard deviation assuming a roughly normal distribution. As above, it's important to note that there is error in any IQ test. I've now had a chance to read the underlying papers related to this thread (which go back at least to 2008), and the IQ tests used in this study are even less mainstream than I feared. "A total of 240 individuals were evaluated with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the Wisconsin Card Sorting Test (WCST)." doi:10.1016/j.bbi.2008.04.156