The Wechsler Intelligence Scale for Children (WISC) has been around since 1949 and is a psychological assessment that measures different aspects of intelligence. Though this test can be used to determine an intelligence quotient (IQ), it is most often used as a clinical tool to measure individual cognitive abilities.
The developers of this test recognize that a child’s performance must be compared to individuals similar to them, and each version of the WISC uses normative samples to compare a child’s score to. Age has the most significant effect on how a child performs on a certain task. Therefore, raw scores of each subtest are calculated and then compared to the normative sample with children of the same age.
This test relies on the idea that cognitive skills, or intelligence, are normally distributed throughout the population. Normal distribution means that most people fall within the average range and less people perform at a range that is above or below average.
Wechsler Intelligence Scale for Children Scoring Explained
Scores for this test are determined based on statistical values such as the mean (the average) and standard deviation (a calculation that determines a significant distance of a score from the average). Once a child’s performance on a subtest is compared to the normative sample, subtest scores are converted into scaled scores that serve as one of the universal metrics for this test.
A scaled score of 10 is the mean and scaled scores that deviate 3 units reflect a standard deviation. Similar subtests are then combined into Primary Index Scales that have a mean of 100 and standard deviation of 15. These numbers help determine the classification for performance.
Classification of performance for scaled scores are as follows:
- Below Average – scaled score 1 to 5
- Low Average – scaled score 6 to 7
- Average – scaled score 8 to 11
- High Average – scaled score 12 to 13
- Superior – 14 to 15
- Very Superior – 16 to 20
Descriptors of performance for standard scores are as follows:
- Below Average – standard score below 79
- Low Average – standard score 80 to 89
- Average – 90 to 109
- High Average – 110 to 119
- Superior – 120 to 129
- Very Superior – above 130
Clinicians use this test for many different reasons and may report all or only some scores. Nevertheless, the following will cover the standard measures offered by the WISC-V, the most recent version of this assessment. It should be noted that there are a number of other analyses beyond the scope of this writing that clinicians may report.
How the WISC is Administered
The fifth version of this test is done individually with the child and clinician and can be done in standard paper-and-pencil administration or on a tablet, digital format. This test includes a total of 16 subtests; however, the standard number of subtests given is 7. Raw scores on these subtests are converted into scaled scores and then the sum of scaled scores of similar tests is converted into a Primary Index Scale.
WISC Index Scales
There are a total of five Primary Index Scales: Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory, and Processing Speed. The Verbal Comprehension Index reflects the ability to access and apply word knowledge. The core subtests include Similarities (how to words are similar) and Vocabulary.
- The Visual Spatial Index reflects the ability to understand visual details and relationships in order to solve puzzles and construct geometric designs. The core subtests are Block Design (orienting blocks to match a picture) and Visual Puzzles (visual spatial integration).
- The Fluid Reasoning Index reflects the ability to detect relationships among visual objects. The core subtests are Matrix Reasoning (reasoning with continuous and discrete visual patterns) and Figure Weights (quantitative reasoning).
- The Working Memory Index reflects the ability to register, maintain, and manipulate visual and auditory information. The core subtests are Digit Span and Picture Span (auditory and visual attention and working memory, respectively).
- The Processing Speed Index reflects the speed at which a child can accurately make decisions. The core subtests are Coding (matching symbols to associated numbers) and Symbol Search (visual scanning and graphomotor speed of matching symbols).
Scores on the five Primary Index Scales are then combined and converted into a Full Scale Intelligence Quotient (FSIQ), which is designed to measure overall intelligence.
Reliability of the Wechsler Intelligence Scale for Children
This test is the gold standard for intellectual assessment for children, partly because of its reliability. Reliability is important because it ensures that test-takers will achieve similar scores each time they take the test. Several studies have measured the reliability of the fifth edition of this test with strong findings, suggesting that the scores a child receives on the subtests and index scales of this test are reliable measurements.