Educational Psychology / Unit 13 EDP 1204 worked example, 60 to 90 seconds
Reading an IQ Score
The idea
Reading an IQ score means locating it on the normal curve. IQ scores have a mean of one hundred and a standard deviation of fifteen. About 34 percent of scores fall between the mean and one standard deviation on each side, 14 percent between one and two, and about 2 percent beyond two. So a score of 115 is one standard deviation above the mean, near the 84th percentile, and a score of 130 is two above, near the 98th. Converting to a z score, the distance from the mean in standard deviations, links IQ to every other standard score.
In practice
Worked example: a student scores 85. That is 15 points, one standard deviation, below the mean: a z of minus 1, near the 16th percentile. A classmate scores 130: a z of 2, higher than about 98 percent of same-age peers, the traditional threshold for giftedness. A score of 70, two standard deviations below the mean, is lower than about 98 percent of peers.
Where people slip
Two standard deviations above the mean is not two percent above it. And an IQ score alone never identifies intellectual disability, which also requires limits in adaptive functioning.
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