Two standard deviations above the mean on an IQ test means that a person got a higher IQ score than 98% of the population would be expected to get (98th percentile). On the Cogat, the mean is set at 100, and each SD, as nono5 pointed out, is 16 points.
One standard deviation above the norm corresponds to the 86th percentile (116). Three standard deviations corresponds to the 99.9th percentile (148).
These numbers work in reverse, too. One standard deviation below the norm is at the 14th percentile (84); two is the 2nd percentile (68), and three is the 0.1th percentile (52).
HTH,
Val
Last edited by Val; 05/03/10 11:41 PM.
