Naglieri Nonverbal Ability Test · reading the report
NNAT scores explained: NAI, percentile rank and stanine
An NNAT3 report gives a Naglieri Ability Index (NAI) from 40 to 160 with an average of 100 and a standard deviation of 16, plus a percentile rank, a stanine and a normal curve equivalent. All of them compare your child with children of the same age. Districts set their own cut-offs.
Which scores does an NNAT3 report show?
Pearson’s NNAT3 manuals describe two raw-to-scale steps and four normative scores. The normative scores are the ones a school compares; the first two are the route to them. All normative scores are based on the child’s age, not grade.
| Score | Scale | Based on | Use |
|---|---|---|---|
| Raw score | Number of the 48 items answered correctly | The level taken | Little meaning alone; converted to a scaled score. |
| Scaled score | One continuous scale across levels | Item difficulty of the level | Compares results across levels and over time; the basis of every normative score. |
| Naglieri Ability Index (NAI) | 40–160; average 100, standard deviation 16 | Scaled score and age | The main ability score; about 68% of the norm sample falls between 84 and 116. |
| Percentile rank | 1–99; 50 is average | Children of the same age | Percentage of same-age children scoring at or below the child; Pearson notes it is often enough when a cut-score is used. |
| Stanine | 1–9; average 5 | Simplified NAI scale | 1–3 below average, 4–6 average, 7–9 above average, in Pearson’s wording. |
| Normal curve equivalent (NCE) | Average 50, standard deviation 21.06 | Same as the NAI | Can be averaged; NCEs of 1, 50 and 99 match percentile ranks of 1, 50 and 99. |
Source: Pearson, NNAT3 Manual Levels A–D and Levels E–G, chapter 2 “Interpretation and Applications”, section “Types of Scores”.
How do you read the Naglieri Ability Index?
The NAI is a normalized standard score. An NAI of 100 is the average for the child’s age, and because the standard deviation is 16, an NAI of 116 is one standard deviation above it. Pearson gives that exact example: an NAI of 116 converts to a percentile rank of 84, so 84 percent of same-age children in the norm sample scored at or below it. At the top of the scale, a percentile rank of 99 covers every NAI from 135 to 160.
The NAI comes from the scaled score and the child’s exact age. Two children with the same number of correct answers can therefore receive different NAIs if they differ in age or took different levels.
Why can percentile ranks mislead?
Percentile ranks are easy to explain, which is why many reports lead with them. Pearson’s manual adds a caution: they are not an equal-interval scale. The ability difference between the 90th and 95th percentile is much larger than between the 50th and 55th, and percentile ranks should not be averaged or subtracted. Use the NAI or the NCE for arithmetic, and the percentile rank for describing where a child stands.
What does a stanine tell you?
Stanines turn the NAI into nine broad bands from 1 to 9, with 5 in the middle. Pearson describes stanines 1–3 as below average, 4–6 as average and 7–9 as above average. Because each band is wide, the stanine is less precise than the NAI, but it is a quick way to talk about a result without over-reading a few points of difference.
What NNAT score qualifies for a gifted program?
Districts set their own cut-offs, and Pearson does not publish one. Its manual uses a 95th-percentile criterion only as an example of how a state or district might apply percentile ranks; it is not a recommended threshold. Some districts screen a whole grade with the NNAT and then review other information, such as achievement, teacher observation or a second ability test. Ask your school which score type it uses, whether it applies national or local comparisons, and what happens after screening.
What should parents do with the result?
- Read the NAI and the percentile rank together; they describe one position on two scales.
- Remember that NNAT norms are by age: a child who is young for the grade is compared with children of the same age.
- Ask about retesting rules. The Levels A–D manual describes two parallel forms with no common items, which some schools use for later testing.
Sources
Questions people ask
What is a good NNAT score?
Pearson does not set a “gifted” score. An NAI of 100 and a percentile rank of 50 are average for the child’s age. Schools and districts decide what result leads to further review and what other information they consider.
What is the Naglieri Ability Index (NAI)?
It is the main NNAT3 score: a normalized scale from 40 to 160 with an average of 100 and a standard deviation of 16, computed from the scaled score and the child’s age. About 68% of children in the norm sample score between 84 and 116.
Is the NAI the same as an IQ score?
No. The NAI is the NNAT3’s own scale, with a standard deviation of 16 and norms based on age. It describes general ability measured with figure problems and should be read as an NNAT result, not converted to another test’s scale.
Why does the report show a scaled score?
The scaled score links the levels of the test on one continuous scale, so results from different levels can be compared and growth can be tracked. The normative scores (NAI, percentile rank, stanine, NCE) are all derived from the scaled score and age.
Are NNAT scores based on grade or age?
The level a child takes is chosen by grade, but Pearson bases the normative scores on age, because the NNAT3 measures ability rather than classroom achievement.
Can a practice app tell me my child’s NAI?
No. A practice app is not normed on a national sample, so its percentages cannot be converted into an NAI or a percentile. NNAT Test Prep reports practice by question type to show where more familiarity helps.