Formal Assessment – the WISC (intelligence test)

One example of a Formal Assessment that assesses cognitive (thinking) ability or intelligence is the WISC.  WISC stands for Wechsler Intelligence Scale for Children.  There are different versions (i.e. WISC – III or IV).

The WISC is an “IQ” or Intelligence Test in which students are assessed on verbal, performance and quantitative ability.

Psychologists may administer the WISC and write a report called a Psychoeducational Assessment (the ‘Psych’ Report).  Teachers do not administer the WISC – but we DO read the reports.

Intelligence Tests  such as the WISC – IV may assess the following psychological processes:

  • A total of five composite scores can be derived with the WISC–IV. The WISC-IV generates a Full Scale IQ (FSIQ) which represents overall cognitive ability, the four other composite scores are Verbal Comprehension index (VCI), Perceptual Reasoning Index (PRI), Processing Speed Index (PSI) and Working Memory Index (WMI).

From the WISC-IV:  Verbal Comprehension Index

  • The Verbal Comprehension Index subtests are as follows:
  • Vocabulary – examinee is asked to define a provided word.
  • Similarities – asking how two words are alike/similar.
  • Comprehension – questions about social situations or common concepts.
  • Information (supplemental) – general knowledge questions.
  • Word reasoning (supplemental)- a task involving clues that lead to a specific word, each clue adds more information about the object/word/concept.
  • The Verbal Comprehension Index is an overall measure of verbal concept formation (the child’s ability to verbally reason) and is influenced by knowledge learned from the environment.

From the WISC-IV: Perceptual Reasoning Index

  • The Perceptual Reasoning Index subtests are as follows:
  • Block Design – children put together red-and-white blocks in a pattern according to a displayed model. This is timed, and some of the more difficult puzzles award bonuses for speed.
  • Picture Concepts – children are provided with a series of pictures presented in rows (either two or three rows) and asked to determine which pictures go together, one from each row.
  • Matrix Reasoning – children are shown an array of pictures with one missing square, and select the picture that fits the array from five options.
  • Picture Completion (supplemental) – children are shown artwork of common objects with a missing part, and asked to identify the missing part by pointing and/or naming.

From the WISC-IV: Processing Speed Index

  • The Processing Speed Index subtests are as follows:
  • Coding – children under 8 mark rows of shapes with different lines according to a code, children over 8 transcribe a digit-symbol code. The task is time-limited with bonuses for speed.
  • Symbol Search – children are given rows of symbols and target symbols, and asked to mark whether or not the target symbols appear in each row.
  • Cancellation (supplemental)- children scan random and structured arrangements of pictures and marks specific target pictures within a limited amount of time.

From the WISC-IV: Working Memory Index

  • The Working Memory Index  (formerly known as Freedom from Distractibility Index) subtests are as follows:
  • Digit Span – children are orally given sequences of numbers and asked to repeat them, either as heard or in reverse order.
  • Letter-Number Sequencing – children are provided a series of numbers and letters and asked to provide them back to the examiner in a predetermined order.
  • Arithmetic (supplemental) – orally administered arithmetic questions. Timed.

From the WISC-IV: Scoring

  • Each of the ten core subtests is given equal weighting towards full scale IQ. There are three subtests for both VCI and PRI, thus they are given 30% weighting each; in addition, PSI and WMI are given weighting for their two subtests each.
  • The WISC-IV also produces seven process scores on three subtests: block design, cancellation and digit span. These scores are intended to provide more detailed information on cognitive abilities that contribute to performance on the subtest. These scores do not contribute to the composite scores.

Scores are reported in the psychoeducational report.  Scores are usually presented as percentiles with descriptions (i.e 35th percentile, low average ability).  See Assessment: Norms, Percentiles, Stanines, Grade Equivalents etc for details.

  • Bell Curve illustrating the range of scores on the Wechsler Adult Intelligence Scale
  • The average score is a range from 85 to 115.  That means most people score between this range.  (That is why the high point of the bell is over these scores).  Fewer people score less than 55 or higher than 145 – that is why the low point of the bell is over these scores.
  • A score of less than 70 indicates low cognitive ability (mild intellectual ability) and a score of less than 55 relates to moderate mental retardation (developmental disability).
  • A score over 130 indicates high cognitive ability and intellectual giftedness (the actual criteria for gifted identification depends on your board)

How does the Test maker know their test is Valid and Reliable?

Psychometric properties of the WISC-IV

The WISC–IV US standardization sample consisted of 2,200 children between the ages of 6 and 16 years 11 months and the UK sample consisted of 780 children. Both standardizations included special group samples including the following: children identified as gifted, children with mild or moderate mental retardation, children with learning disorders (reading, reading/writing, math, reading/writing/math), children with ADHD, children with expressive and mixed receptive-expressive language disorders. children with autism, children with Asperger’s syndrome, children with open or closed head injury, and children with motor impairment.

WISC–IV is also validated with measures of achievement, memory, adaptive behaviour, emotional intelligence, and giftedness. Equivalency studies were also conducted within the Wechsler family of tests enabling comparisons between various Wechsler scores over the lifespan. A number of concurrent studies were conducted to examine the scale’s reliability and validity. Evidence of the convergent and discriminant validity of the WISC–IV is provided by correlational studies with the following instruments: WISC–III, WPPSI–III, WAIS–III, WASI, WIAT–II, CMS, GRS, BarOn EQ, and the ABAS–II. Evidence of construct validity was provided through a series of exploratory and confirmatory factor-analytic studies and mean comparisons using matched samples of clinical and nonclinical children.

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