Prevalence of Low Scores on the WISC-IV-HR: Are the Low Scores Always a Reason for Concern?

The fourth edition of the Wechsler Intelligence Scale for Children (WISC-IV) was published in 2003. and it quickly became one of the world’s most used measures of intelligence for children and adolescents. Adaptation and standardization for the Croatian language, in 2009, made this test available for experts to assess the level of intelligence of children in Croatia, but for the interpretation of individual achievement to be accurate, there is a need to consider the overall prevalence of low subtest and Index scores in healthy children. Understanding the prevalence of obtaining low scores on a particular test battery provides an estimate of the probability that a specific result obtained by the clinician is clinically significant and unusual for the normative population. The aim of the study was to examine the prevalence of low scores on the WISC-IV-HR subtests and Indexes in overall Croatian standardization sample and depending on child’s intelligence level. The study included 1200 children and adolescents aged between 6 years 0 months and 16 years 11 months. The results show that even when considering a cut-off more than 2 SD below the mean, 1 out of 5 children obtains at least one low WISC-IV subtest score. The prevalence of low Index scores is smaller but still should not be ignored while interpreting test results. Also important to keep in mind is that those results cannot be explained only by the overall level of child’s intelligence since even using the most rigorous cut-off value, around 1 out of 10 children with average or higher intelligence level will obtain low subtest scores and around 3% of them will have one low Index score. Keywords: intelligence, Croatian adaptation, WISC-IV, low scores