While people often talk about test scores, many people are confused about exactly what these test scores mean. In order to adequately assess and interpret test scores, psychometritians use a process known as standardization. The standardization process involves administering the test to a representative sample of the entire population that will eventually take the test. Each test taker completes the test under the same conditions as all other participants in the sample group. This process allows psychometricians to establish norms, or standards, by which individual scores can be compared.
Intelligence test scores typically follow what is known as a normal distribution, a bell-shaped curve in which the majority of scores lie near or around the average score. For example, the majority of scores, which is about 68%, on the WAIS-III tend to lie between plus 15 or minus 15 points from the average score of 100. As you look further toward the extreme ends of the distribution, scores tend to become less common. Very few individuals receive a score of more than 145 or less than 55 on the test.
As described in chapter 9 of our textbook, the following is a rough breakdown of various IQ score ranges. However, it is important to remember that IQ tests are only one measure of intelligence. Many experts suggest that other important elements contribute to intelligence, including social and emotional factors.
115 to 129 - Above average; bright
130 to 144 - Moderately gifted
145 to 159 - Highly gifted
160 to 179 - Exceptionally gifted
180 and up - Profoundly gifted
Intelligence tests (also called instruments) are published in several forms:
Group intelligence tests usually consist of a paper test booklet and scanned scoring sheets. Group achievement tests, which assess academic areas, sometimes include a cognitive measure. In general, group tests are not recommended for the purpose of identifying a child with a disability. In some cases, however, they can be helpful as a screening measure to consider whether further testing is needed and can provide good background information on a child's academic history.
Individual intelligence tests may include several types of tasks and may involve easel test books for pointing responses, puzzle and game-like tasks, and question and answer sessions. Some tasks are timed.
Computerized tests are becoming more widely available, but as with all tests, examiners must consider the needs of the child before choosing this format.
You can find more information about the types of intelligence tests by clicking here.
The bell curve is a very interesting concept. Although it is incredibly useful in determining the statistics of a population, it isn't always necessarily ideal. This curve that accounts for up to four standard deviations wouldn't be effective when the data is skewed due to the difficulty of the test. For example, if it were skewed to the left (lots of high test scores), then this curve wouldn't be nearly as helpful.