Long-term stability of the French WISC-IV: Standard and CHC index scores

Introduction

The assumption of the stability of intelligence is the source of the predictive value of the Intelligence Quotient (e.g., Full Scale IQ). However, few studies have investigated the long-term stability of one of the most frequently used tests in the field of cognitive assessment: the Wechsler Intelligence Scale for Children – 4th edition (WISC-IV).

Objective

For a deeper understanding and a better use of intelligence test scores, this study examined the long-term stability of the standard index scores and five CHC composite scores of the French WISC-IV.

Method

A test–retest procedure was used, with an average retest interval of 1.77 year (SD = 0.56 year). This study involved 277 French-speaking Swiss children aged between 7 and 12 years. Three types of stability analysis were conducted: (a) mean-level changes, (b) rank-order consistency and change, and (c) individual-level of change.

Results

The observed pattern of mean-level changes suggested a normative mean-level stability for the Verbal Comprehension Index (VCI), the Perceptual Reasoning Index (PRI), the General Ability Index (GAI), Comprehension-Knowledge (Gc), and Visual Processing (Gv). Regarding individual differences stability, only the FSIQ and the GAI reached a reliability of .80 required for making decisions about individuals. Using a two standard errors of measurement confidence interval (± 2 SEM), we examined individual-level stability. Results indicated that more than 70% of the children presented stable performances for the GAI, Gc, and Gv scores.

Conclusion

Together, nomothetic and idiographic perspectives suggested that the GAI, Gc, and Gv were the most stable scores in our non-clinical sample.