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Individual intelligence tests can be given only by specially trained psychologists. Such tests are expensive and time-consuming to administer, and so educational institutions often use tests that can be given to a group of people at the same time. Commonly used group intelligence tests include the Otis-Lennon School Ability Test and the Lorge-Thorndike Intelligence Test.
Some researchers have suggested that biological indices such as reaction time and perceptual speed relate to intelligence as measured by IQ tests:
Many psychologists believe that cultural bias can affect intelligence tests, for the following reasons:
Some characteristics of IQ tests are standardization, norms, percentile scores, standardization samples, reliability, and validity.
Intelligence tests are standardized, which means that uniform procedures are used when administering and scoring the tests. Standardization helps to ensure that people taking a particular test all do so under the same conditions. Standardization also allows test takers to be compared, since it increases the likelihood that any difference in scores between test-takers is due to ability rather than the testing environment. The SAT and ACT are two examples of standardized tests.
Researchers use norms when scoring the tests. Norms provide information about how a person’s test score compares with the scores of other test takers. Norms allow raw test scores to be converted into percentile scores. A percentile score indicates the percentage of people who achieved the same as or less than a particular score. For example, if someone answered twenty items correctly on a thirty-item vocabulary test, he receives a raw score of 20. He consults the test norms and finds that a raw score of 20 corresponds with a percentile score of 90. This means that he scored the same as or higher than 90 percent of people who took the same test.
Psychologists come up with norms by giving a test to a standardization sample. A standardization sample is a large group of people that is representative of the entire population of potential test takers.
Most intelligence tests have good reliability. Reliability is a test’s ability to yield the same results when the test is administered at different times to the same group of people. For more on reliability, see page 14.
Validity is a test’s ability to measure what it is supposed to measure. For more on validity, see page 14. Although intelligence tests cannot be considered good measures of general intelligence or general mental ability, they are reasonably valid indicators of the type of intelligence that enables good academic performance.
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