IQ percentiles and the Wechsler Intelligence Scale for Children (WISC)

The Wechsler Intelligence Scale for Children (WISC) is an intelligence test for children between age 6-16 that can be completed without reading or writing. Tests include Vocabulary – straightforward questions over meaning of words, Matrix reasoning – children are shown an array of pictures with one missing square and select the picture that fits from 5 options and Letter / Number sequencing. The WISC generates an IQ score.

The IQ percentile table below illustrates the IQ score and the corresponding percentile rank. A percentile rank shows the percentage of people that scored above and below a certain score. For example, the 50th percentile means 49 out of 100 per cent of the people who took the test scored higher scores and 49 got lower scores. The 5th percentile means 75 out of 100 scored higher and 25 scored lower.

The IQ scale only goes as low as 45. A percentile score of less than 1 equates to an IQ score of 65.

The WISC is used both as an intelligence test and a clinical tool. It can be used to show discrepancies between a child’s intelligence and their performance at school and it is this discrepancy that Educational Psychologists look for when using this test.