Name: normal distribution in intelligence scores
Uploaded: 2025-01-08T16:31:10.000Z
Duration: 1 min 21 s
Channel: JoVE

A bell curve, or normal distribution, is a symmetrical, bell-shaped graph showing how data points are distributed around the mean.
Many human traits, such as height, naturally follow the bell curve distribution.
Theoretically, the bell curve is mathematically defined and smooth, reaching its peak at the center. It tapers symmetrically on both sides, approaching the X-axis without ever touching it.
For example, most intelligence tests have a mean score of 100, with each standard deviation or SD equalling 15 points, showing how scores are spread across the population.
A score of 85 is one SD below the mean, and 115 is one SD above. Scores ranging from 85 and 115 are considered average, including about 68% of the population.
Approximately 2.2% of the population scores over two SDs above the mean, 130 or higher, indicating superior intelligence.
Conversely, around 2.2% of the population scores more than two SDs below the mean, 70 or lower, which may indicate an intellectual disability.

the bell curve

The Bell Curve

The normal probability distribution, often depicted as a symmetrical, bell-shaped curve, is fundamental in statistics and the study of natural phenomena. This pattern, famously described by mathematician Carl Friedrich Gauss, shows how data points are distributed around a central mean, with most values near the average and fewer observations occurring as they deviate further from it.
This pattern applies to many human characteristics beyond intelligence, such as height. For example, if you measured the heights of a large group of women, most would fall within the average range, while fewer would represent extreme heights. The normal curve is mathematically defined, smooth, and continuous, peaking at the mean value and tapering symmetrically as it approaches the extremes. However, the curve&#39;s tails never touch the X-axis, representing that extreme, rare values are still possible.
Features of the Normal Distribution
In the context of intelligence testing, many tests are designed to follow a normal distribution, with a mean score of 100 and a standard deviation (SD) of 15. The SD measures how much scores deviate from the mean. In this distribution, approximately 68% of scores fall within one SD of the mean, ranging from 85 to 115. These scores are considered to represent the average intelligence range for the population.
Application in Intelligence Testing
Beyond the average range, more extreme scores are found. For instance, scores that fall more than two SDs above or below the mean represent about 2.2% of the population on each side. A score of 130 or higher, two SDs above the mean, indicates superior intelligence. Conversely, a score of 70 or lower, two SDs below the mean, may indicate intellectual disability. This symmetrical distribution of intelligence scores provides a statistical framework for understanding variations in cognitive ability within a population.

A bell curve, or normal distribution, is a symmetrical, bell-shaped graph showing how data points are distributed around the mean.
Many human traits, such ...

Education

JoVE Core

Introduction to Psychology

Unit 1

Thinking, Language And Intelligence

KEY TERMS AND CONCEPTS

normal distribution in intelligence scores

The normal distribution is a bell-shaped pattern used to describe many kinds of data, including intelligence test scores. It is symmetrical, with most values clustered around the mean, or average, and fewer values found farther from the center. Mathematician Carl Friedrich Gauss is closely linked to this pattern.

This curve also appears in many natural measurements beyond intelligence, such as height. If a large group of women were measured, most heights would fall in the middle range. Fewer people would be very short or very tall. The normal curve is smooth, continuous, and mathematically defined. It peaks at the mean and tapers evenly toward both extremes.

The tails of the curve never touch the X-axis. That shows that very rare values can still occur. In intelligence testing, many scores are designed to follow this pattern. These tests often use a mean of 100 and a standard deviation, or SD, of 15. The SD shows how far scores usually spread from the mean.

About 68% of scores fall within one SD of the mean, from 85 to 115. This range is usually considered average intelligence in the population. Scores farther from the center are less common. Scores more than two SDs above or below the mean make up about 2.2% of the population on each side.

A score of 130 or higher is two SDs above the mean and suggests superior intelligence. A score of 70 or lower is two SDs below the mean and may indicate intellectual disability. This symmetrical score pattern helps statisticians understand how cognitive ability varies across a population.

Normal Distribution in Intelligence Scores

normal-distribution-in-intelligence-scores

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wechsler's contribution to measures of intelligence

wechsler-s-contribution-to-measures-of-intelligence

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The normal distribution is a bell-shaped pattern used to describe many kinds of data, including intelligence test scores. It is symmetrical, with most values clustered around the mean, or average, and fewer values found farther from the center. Mathematician Carl Friedrich Gauss is closely linked to this pattern. This curve also appears in many natural measurements beyond intelligence, such as height. If a large group of women were measured, most heights would fall in the middle range. Fewer...

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key terms and concepts

Learn how the normal distribution models intelligence test scores, with a mean of 100, standard deviation of 15, and rare scores at both extremes.

Normal Distribution in Intelligence Scores | JoVE K12

JoVE Core Introduction to Psychology offers an engaging learning experience on the fundamental principles of psychology through concise video lessons. Students will explore important topics such as cognitive processes, emotional regulation, and neural mechanisms, establishing a strong foundation in the study of the mind and human behavior. This series provides an accessible and captivating approach to grasp the essential concepts of the discipline.

introduction to psychology

Normal Distribution in Intelligence Scores

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