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# Intellectual Development (page 4)

### Standard Deviation

Psychologist David Weschler,  1896-1981 developed two well-known intelligence scales:  the  Wechsler Adult Intelligence Scales (WAIS) and the Wechsler Intelligence Scale for Children (WISC).  These are often used today instead of the Stanford-Binet. Scoring on all tests is similar.

Weschler also did work on the scoring of tests, and the use of standard deviations.  A standard deviation is a “degree of probable error”.

If you scored 108 on a test, and the standard deviation for that particular test was 3 points, that means your score could be as much as 3 points lower or as much as 3 points higher.

When calculating standard deviation, take the score + or –  the deviation.

### Mean and Average

When working with statistics and comparing one individual’s test scores to other individuals or a group, it is helpful to calculate “mean” and “average” scores.

A “mean” score is the middle score in the entire range of possibilities.  You would take all the scores in a sample group;  line them up in order of low to high, and find the middle.

An “average” score is when you add together all the scores in a sample group, and then divide by the total number of samples.

“Mean” and “average” scores for any one test group may or may not be the same.  Can you determine the mean and average scores for a group with the following individual test scores?
Answer: 106 is the mean score;  105.8 is the average score

### Mental Handicap

When the Stanford-Binet was developed, individuals scoring below 70 were called “mentally deficient”, and the 4 levels of deficiency were labeled from least to most severe as “borderline deficiency, moron, imbecile, and idiot”.  Society’s misuse of those terms eventually led to a change. The term “mental retardation” replaced “deficient”, and the words “mild, moderate, severe and profound” replaced previous labels.

Today, the term “mental retardation” has been replaced with “mental handicap”.  Mildly mentally handicapped individuals are considered educable.  Moderately handicapped individuals are considered trainable.

Name changes have occurred to reinforce the idea that all human beings have value within American society, as well as general  acceptability. Even the upper scores have been changed from “superior” labels to “gifted” and “high ability learners”.

 IQ Range Classification 50-69 Mild 35-49 Moderate 20-34 Severe below 20 Profound

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