Stability of the WISC-IV in a sample of elementary and middle school children.

This study investigated test-retest stability of the Wechsler Intelligence Scale for Children, Fourth Edition, in 43 elementary/middle school students tested on two occasions approximately 11 months apart. Subtest stability coefficients ranged from .26 (Picture Concepts) to .84 (Vocabulary [VC]). Composite stabilities ranged from .54 (Processing Speed Index) to .88 (Full Scale Intelligence Quotient [FSIQ]). On 11 subtests and three indexes, the standardization sample stability coefficients were significantly larger than those of the present sample, with only the VC subtest and FSIQ having high levels of test-retest stability. Mean practice effects were not significant, but range of gain or loss for some individuals was large. On the FSIQ, 42% changed > +/-5 points on retest. The FSIQ is less stable than one might infer from the large stability coefficient and small mean practice effect.