Validation of the NIH Toolbox Cognitive Battery in intellectual disability

The z scores on each test (representing group performance relative to the general population average performance) are shown, derived from the mixed-model analysis of variance, adjusted for IQ. A z score of 0 (horizontal line at top) represents the average performance in the general population normative sample. The z scores <0 represent the number of SDs below the general population average for the chronologic age band. Error bars represent 95% confidence intervals. *Comparison between fragile X syndrome (FXS) and intellectual disability (ID) of other or unknown cause. †Comparison between FXS and Down syndrome. *p < 0.05; **p < 0.01; ***p < 0.001; †p < 0.05; ††p < 0.01; †††p < 0.001. DCCS = Dimensional Change Card Sort; LS = List Sorting Working Memory; OR = Oral Reading and Recognition; PC = Pattern Comparison Processing Speed; PSM = Picture Sequence Memory; PVT = Picture Vocabulary.