The stability of WAIS-R IQ for 16-year-old students retested after 3 and 8 months

The stability of Wechsler Adult Intelligence Scale-Revised IQs was investigated for 52 students 16 years of age. Half of the subjects were retested after a 3-month interval; half after an 18-month interval. Stability coefficients were uniformly high for both retest intervals. Gains in Verbal, Performance, and Full Scale IQ over 3 months were similar to practice effects reported for adult subjects. However, IQs for males retested after 18 months increased beyond the practice effect. Females retested after 18 months showed the same result only on Verbal IQ. The findings remind clinicians of the important distinction between relative and absolute stability, especially for 16-year-old students tested with the WAIS-R.