Pick a group. About 9% of it scores here or lower.
People cluster with others of similar ability at school, at work and among friends, so the full curve is rarely visible in any one group. It's still there.
80 sits nearly a full standard deviation above the clinical line
−1.33 SD, about the 9th percentile. Low average: the lower end of the normal range, not a borderline disability and not a clinical label.
Not "can't" but "needs it concrete, broken down and with a bit more time"
An IQ is an average across several abilities, so 80 rarely means uniformly slow. Concrete, practical thinking is usually intact. What's harder is holding several things in mind at once, reasoning about the hypothetical, and solving new problems fast. The strategies that help are the ones that lower that load. They're how anyone learns a hard skill, made non-optional.
Ability matters most in complex, novel jobs, and least in learnable, repeatable ones
Large syntheses of job-performance research, including Hunter and Schmidt's, find that cognitive ability predicts performance most strongly when work is complex and changing, and much less when it's structured and repeatable. That second group is large, and mastery there comes from doing the thing many times.
Many of these pay well and grow with experience, and they reward reliability, steadiness and physical skill, none of which an IQ test measures.
The number sets a slope, not a ceiling. Effort changes the slope.
Why conscientiousness can outweigh a 20-point gap
Being dependable, organised and persistent predicts job performance independently of cognitive ability, and in many roles about as strongly. Terman's long study of high-IQ children found that the most successful adults were distinguished less by score than by persistence and drive.
Turning up on time, finishing what you start, being trusted with money and tools: an IQ test measures none of it, and all of it compounds over a career.
The military's floor sits right around 80
US enlistment uses the AFQT percentile from the ASVAB. Federal law bars enlisting anyone in Category V, below the 10th percentile, and each branch sets its own minimum above that. On a normal curve the 10th percentile corresponds to an IQ of about 81, so 80 sits right at the line.
This floor came from experience with very low-scoring recruits, including Project 100,000 in the late 1960s. Training failure was much more common. It is a threshold for quick, time-pressured technical training, the kind of task that is hardest at this score.
A delivery van uses 1 gallon of fuel every 12 miles. The route is 60 miles. The van starts with 3 gallons. How many more gallons does the driver need?
We calculate percentiles, rarity and AFQT conversions from a normal distribution with mean 100 and SD 15. The occupational, Terman and military-history sections summarise published research rather than this site's data. Group counts are expected values, so real groups vary.