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Understanding psychological test scores and terminology

This article will help the reader further understand commonly used test scores used in psychological and educational testing. These include: Standard Scores, Percentiles, Age/Grade Equivalents, Confidence Intervals, Bands of Error, and the Bell Curve.

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Understanding Test Scores

Most psychological tests are reported using standard scores and percentiles. Standard scores describe how an individual performed on that test, compared to people the same age in the norm group. The norm group is the group of people (usually in the thousands) that the test is administered to during test development. Because all tests inherently come with error (which can be due to fatigue, lighting, sounds during testing, and an infinite number of other factors), they are sometimes reported as falling in a confidence interval. A confidence interval is a range that the score is likely to fall in, based on the confidence level used (usually 68%, 95%, or 99%). The lower the band of error (68% is the lowest typically used, while 95% is used most often), the smaller the range of scores. Band of error is the percentage of confidence at which we can be confident that a person's true score (what they would score on the test given ideal setting and other factors) falls within the given range. For example, If John scored a standard score of 100 on an IQ test, we can be 95% confident that his true score falls ...

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Discussion and explanation of psychological and educational testing scores and descriptors.