How Reliable Is The Wechsler IQ Test

How Reliable Is The Wechsler IQ Test


Measuring someone’s intelligence is difficult to do.  In many ways, we need to think abstractly about intelligence.  Can we measure the intelligence of a person by looking at their grades in school?  Maybe someone was very intelligent but did not have the motivation to study.  Can we measure intelligence by how well someone can communicate and cohabitate with others, otherwise known as social intelligence?  Perhaps the person in question is very smart, but is awkward in these situations.  Intelligence Quotient (IQ) tests are usually used in situations where intelligence must be measured, and one of the most popular is the Wechsler Intelligence test.

What is the Wechsler Intelligence Test?

This test is administered in several parts, using different scales and different subtests.  Some of the scales used are perceptual reasoning, verbal, working memory, and processing speed. There are different types of Wechsler tests for different age groups, each using the average scale of 100 points, which is the mean of the normal curve.  One of the advantages this test has over other IQ tests, such as the Stanford Binet IQ test, is that it allows analysis of a profile of scores rather than just one intelligence quotient.  Each section of the test can be analyzed individual to paint a better picture of a person’s intelligence.  These intelligence tests have stood the test of time, staying useful after several years of clinical trials and research.  There have been several allegations that these tests may be reliable in theory, but in practice the scores vary widely.

Is the Test Really Reliable?

Research has shown that the Wechsler test is one of the most well-designed tests to measure intelligence.  It provides a wide profile of indexes and scales and really allows for the diagnosis of certain mental complications, as well as an accurate depiction of a person’s intelligence.  However, as most tests of this nature are, the tests are only as reliable as the person giving them.

Unlike several easily administered intelligence tests, most testing centers still use physical bodies, both psychologists and doctors, to administer the test.  This brings human error into play, which is more or less reduced to nothing when a test is administered on a computer.  There have been several reports of testers being either very liberal or very conservative when giving points for certain test sections.  A study completed at Central Missouri State University had thirty eight graduate students and psychologists score test subjects in several different groups.  What the study found was that while the mean IQ and indexes were similar across groups, there were large variances in the ranges of Verbal IQ, Performance IQ, and Full Scale IQ, indicating that the ability to consistently administer this test should be called into question.

There have also been reports of certain subtests being left out of the testing altogether due to time and cost constraints.  While administering only a few of the subtests will allow a test administrator to estimate an IQ close to what the real IQ is, administering the testing this way tends to be less accurate than the administrator thinks.

The methodology and purpose of the Wechsler Intelligence Scale is sound, but it needs to be administered correctly and consistently in order for the results to be reliable.


For all official Wechsler materials, visits Pearson Clinical.