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What Is the Average IQ?

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Normal Distribution Image courtesy Alessio Damato

Question: What Is the Average IQ?

Answer:

Intelligence tests are one of the most popular types of psychological tests in use today. On the majority of modern IQ tests, the average (or mean) score is set at 100 with a standard deviation of 15 so that scores conform to a normal distribution curve. This means that 68 percent of scores fall within one standard deviation of the mean (that is, between 85 and 115), and 95 percent of scores fall within two standard deviations (between 70 and 130).

Why is the average score set to 100? Psychometritians utilize a process known as standardization in order to make it possible to compare and interpret the meaning of IQ scores. This process is accomplished by administering the test to a representative sample and using these scores to establish standards, usually referred to as norms, by which all individual scores can be compared. Since the average score is 100, experts can quickly assess individual test scores against the average to determine where these scores fall on the normal distribution.

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