What Is an IQ Test? A Beginner’s Guide.

IQ tests are among the most widely known achievements in psychology. They are also one of the most debated tools in psychology, education, and even popular culture. They aim to measure human intelligence, a concept that has fascinated scholars, scientists, and the general public for centuries. This article delves into what IQ tests are, why they matter, the mathematical principles underpinning them, the meaning behind different IQ score ranges, and the reasons someone might want to take one.

Some Basics

An IQ test is a standardized assessment designed to evaluate a person’s cognitive abilities compared to a representative population. These tests measure a variety of mental skills, including reasoning, problem-solving, memory, spatial awareness, and verbal comprehension.

IQ tests typically consist of multiple indexes that test different cognitive abilities. So, it is often the case that your results contain more than just an IQ score after completing an IQ test. Some IQ tests test more cognitive abilities than other. For example, the RIOT tests 5 cognitive abilities:

1. Verbal reasoning: Understanding language-based problems, such as analogies or vocabulary.

2. Fluid reasoning: Solving puzzles or identifying patterns, often with shapes or numbers.

3. Working memory: Recalling sequences or manipulating information mentally.

4. Processing speed: Completing tasks quickly and accurately.

5. Spatial Ability: Perceiving and manipulating spatial relationships..

Some of the most well-known IQ tests include the Wechsler Adult Intelligence Scale (WAIS), the Stanford-Binet Intelligence Scales, the Raven’s Progressive Matrices, and others you can read about here. While these tests have different types of questions and subtests, their core purpose remains the same: to quantify intellectual capacity.

Lastly, to wrap up the basics, watch the first 1-2 min of this video where Richard Haier defines IQ score, general intelligence (a.k.a. "g"), and intelligence:

Why Are IQ Tests Important?

IQ tests hold significance for several reasons, spanning practical, scientific, and societal domains:

Educational Placement:

Schools often use IQ tests to identify students who may need special education services, whether for gifted programs or learning disabilities. A high or low score can guide teachers in tailoring instruction to a student’s needs.

Scientific Research:

IQ scores provide a standardized metric for studying intelligence across populations, exploring its links to genetics, environment, education, and even health outcomes. Research consistently shows IQ correlates with academic success, job performance, and socioeconomic status. Cognitive abilities research can spill over into other cognitive science research where IQ data can be way more useful than you might think. Examples of these use cases can be seen in articles such as "Studying IQ Matters" or even "Significantly Enhancing Adult Intelligence With Gene Editing May Be Possible".

Career and Occupational Insight:

Employers and military organizations historically used IQ-style assessments (like the U.S. Army’s aptitude tests during World War I) to match individuals with roles suited to their cognitive strengths. While less common today, certain fields—such as engineering or academia—still value the skills IQ tests measure.

Personal Understanding:

For individuals, an IQ test can offer insight into cognitive strengths and weaknesses, fostering self-awareness or guiding personal development.

Despite their utility, IQ tests are not without criticism. Some argue they fail to capture creativity, emotional intelligence, or cultural differences, sparking ongoing debates about their fairness and scope. You may argue this effectively, but it is hard to argue against how correlated IQ is to so many life outcomes. It really is fascinating.

The Math Behind IQ Tests

IQ scores are rooted in statistical principles, the score itself reflects how an individual’s performance compares to a normative population. Here’s how it works:

Raw Scores and Standardization:

When you take an IQ test, you receive a raw score based on the number of correct answers. This score is meaningless on its own—it must be compared to a larger group. Test developers administer the test to a representative sample (thousands of people) to establish norms.

The Bell Curve:

IQ scores follow a normal distribution, often called a bell curve. In this distribution:

The average (mean) score is set at 100. The standard deviation (SD), a measure of score variability, is typically 15 points (on tests like the WAIS or Stanford-Binet). A normal distribution means:

• 1. About 68% of people score within one SD of the mean (85–115).

  2. About 95% score within two SDs (70–130).

  3. Only 2.5% score below 70 or above 130.

Calculating IQ

Originally, IQ was calculated as a ratio:

For example, a 10-year-old performing like a 12-year-old would have an IQ of 120. Modern tests, however, use deviation IQ, where your score is based on how far you deviate from the mean of 100, adjusted for age.Mathematically:

IQ=100+(Z×SD)

Where ( Z ) is your standardized score (how many standard deviations you are from the mean), and SD is 15. A ( Z ) score of +1 (one SD above average) yields an IQ of 115.

If you want to dive deeper, read this whole article on "How To Calculate IQ" that we wrote previously. Moving along. A common question…

What Do IQ Ranges Mean?

IQ scores are categorized into ranges, each with implications for cognitive ability. Here’s a breakdown based on a standard deviation of 15. In this breakdown we are also assuming the IQ test taken was the RIOT:

<= 74 : Uncertain Score - Bottom 4%

This score is outside of the range that the RIOT is designed to measure accurately. If you had problems with taking the test (such as struggles reading English or technical difficulties), then this score may not be accurate. You may need to take an intelligence test given face-to-face for an accurate IQ score.

75-80 : Foundational Score - 5%

This range means that you have a level of intelligence that you can build on in life. People in this range often graduate from high school, hold a steady job, and enjoy a successful family life. Typical jobs for people in this range include materials handler, packer, and custodian.

81-90 : Approaching Average Score - 16%

This range is approaching the average score range. Most people with scores in this range graduate from high school, and some attend vocational training or college. People in this range can master the skills needed for jobs that are “hands on.” You would likely succeed in on-the-job training with opportunities to practice new skills. Typical jobs in this range include nurse’s aide, warehouse worker, and assembler.

91-99: Average Score - 25%

This range is in the range of typical scores. Almost everyone with a score in this range graduates from high school, and many also finish vocation training or attend college. People in this range can master skills for many jobs.Typical jobs in this range include receptionist, cashier, machinist, security guard, and mechanic.

100–109: Average Score - 25%

This range is in the range of typical scores. Almost everyone with a score in this range graduates from high school, and many successfully complete vocational training or college. People in this range can quickly learn many new job skills and may need little supervision. Typical jobs in this range include teacher, drafter, laboratory technician, customer service technician, police officer, and nurse.

110-120: Above Average Score - 16%

This range is above average. Many people in this range attend and graduate from college, and many earn postgraduate degrees. People in this range can quickly learn complex or abstract information. They can also create and execute long-term plans, such as planning for retirement or starting a business. Typical jobs in this range include attorney, chemist, engineer, physician, and auditor.

121-135: Significantly Above Average Score - 8%

This range is significantly above average. Most people in this range attend and graduate from college, and many earn postgraduate degrees. People in this range learn complex or abstract information much more quickly than many of their peers. They can also create and execute long-term plans, such as planning for retirement or starting a business. People with IQs in this range have the ability to master the information and skills needed for almost any job. As a result, other cognitive abilities (e.g., verbal ability spatial ability) and interests are often a determining factor in choosing a career. Many rise to positions of leadership in their company or discipline.

136+: Far Above Average Score - Top 1%

This range is the top 1% of the population. Most people in this range graduate from college, and many earn postgraduate degrees. People in this range learn complex or abstract information so quickly that it appears to others that they naturally just “catch on.” They often create and execute long-term plans, such as planning for retirement or starting a business. People with IQs in this range have the ability to master the information and skills needed for almost any job. As a result, other cognitive abilities (e.g., verbal ability spatial ability) and interests are often a determining factor in choosing a career. As a result, other cognitive abilities (e.g., verbal ability spatial ability) and interests are often a determining factor in choosing a career. Many innovators and creators in society have IQs in this range.

And That's All For a Beginner's Guide

Let's keep this one short. There is a lot more to be said about IQ tests, which we will cover in "A Comprehensive Guide to IQ Tests" article soon. Ultimately, IQ tests are powerful, but take them with a grain of salt. There are numerous other qualities vital to good life outcomes. Moreover, a single score can’t define a person’s worth. I know you probably know this already, but I want to reiterate it just to be sure.

Ciao for now.