What is the distribution of IQ scores?
IQ score ranges
| IQ scale | Interpretation of IQ score | % of population |
|---|---|---|
| 111-120 | Above average intelligence | 15.7% |
| 90-110 | Average intelligence | 51.6% |
| 80-89 | Below average intelligence | 15.7% |
| 70-79 | Cognitively impaired | 6.4% |
Are IQ scores normally distributed?
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. About 68% of individuals have IQ scores in the interval 100 ± 1 ( 15 ) = [ 85 , 115 ] . About 99.7% of individuals have IQ scores in the interval 100 ± 3 ( 15 ) = [ 55 , 145 ] .
What percentage of the population has an IQ between 100 and 115?
34.13%
115 is one standard deviation above the mean, i.e., z = 1.0. So, by the table, 34.13% of the population has an IQ score between 100 and 115. Since 50% is supposed to be above the average of 100 (by symmetry), this means 50 – 34.13 = 15.87 (%) has an IQ score above 115. Similarly, 130 corresponds to z = 2.0.
Can test scores be normally distributed?
Therefore, this student scored better than 99.87% of the other test-takers. This statistic is also referred to as a percentile. Of course not all test score distributions are normally distributed. However, standardized tests are designed sothat the outcome follows a normal distribution curve.
What standard score is 1.5 SD below the mean?
| Standard Deviation/Standard/Scaled Score Correspondence | ||
|---|---|---|
| Standard Deviation (SD) | Standard Score | Scaled Score |
| 1 SD below mean | Between 70 and 85 | Between 4 and 7 |
| 1.5 SD below mean | 77.5 | 5.5 |
| 2 SD below mean | 70 or below | 4 or below |
How are scores determined on the Wechsler Intelligence Scale?
Wechsler Intelligence Scale for Children Scoring Explained Scores for this test are determined based on statistical values such as the mean (the average) and standard deviation (a calculation that determines a significant distance of a score from the average).
What’s the standard deviation of the Wechsler IQ test?
The Wechsler tests have a standard deviation of 15 while the Stanford-Binet tests have a standard deviation of 16, meaning what constitutes an average IQ score on each is slightly different, and also it makes for a slightly wider distribution if you were to graph the Stanford-Binet’s IQ bell curve compared to that of the Wechsler test.
When did Wechsler come up with the WAIS test?
As a result, Wechsler devised a new test during the 1930s, known as the Wechsler-Bellevue Intelligence Scales. The test was later revised and became known as the Wechsler Adult Intelligence Scale, or WAIS.
What are the scores on the Wechsler Verbal Comprehension Index?
Verbal Comprehension Index This index reflects an individual’s ability to understand, use and think with spoken language. It also demonstrates the 110 to 119 High Average 75 – 90 90 to 109 Average 25 – 73 80 to 89 Low Average 9 – 23 70 to 79 Borderline 2 – 8 69 & below Intellectual Disability .01 – 2