Intelligence Tests

Intelligence is often defined as a measure of general mental ability. Of the standardized intelligence tests, those developed by David Wechsler are among those most widely used. Wechsler defined intelligence as “the global capacity to act purposefully, to think rationally, and to deal effectively with the environment.” While psychologists generally agree with this definition, they don't agree on the operational definition of intelligence (that is, a statement of the procedures to be used to precisely define the variable to be measured) or how to accomplish its measurement.

Test construction. To be useful, tests, including intelligence tests, must be constructed using the established criteria of standardization, reliability, and validity.

• Standardization is the process of making uniform and objective both testing procedures and scoring procedures in order to obtain meaningful scores. Scores on standardized tests are interpreted in reference to scores obtained from a standardization sample, that is, scores from a comparable group of subjects tested under appropriate conditions.

• The term reliability refers to the consistency of results. Reliability of a test is determined by one of the following methods.

  • test and retest reliability: comparison of original test scores with retest scores

  • alternate form reliability: comparison of scores obtained on alternate forms of a test

  • split-half reliability: comparison of scores obtained on two halves of tests (such as scores on odd- versus even-numbered questions)

• The term validity refers to the extent that a test measures what it is supposed to measure. Types of validity include

  • content validity: the extent to which a test reflects a sample of the behavior to be measured

  • predictive validity: the extent to which a test can predict a person's behavior in another situation

  • face validity: how appropriate a test “appears” to be, just from the way the items read

  • construct validity: how well a test assesses the construct (for example, intelligence) for which it was designed

  • concurrent validity: how well the results of a test agree with those of a new test or a different form of the test measuring for the same construct (for example, intelligence)

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