Plain-English definitions for every term you'll encounter preparing your child for gifted, IQ, and admissions tests.
Ability Index
A standardized score (mean 100, SD 15) used by many gifted tests including the NNAT (NAI) and OLSAT (SAI). Comparable to an IQ score in format and interpretation.
Adaptive Testing
A test format where question difficulty adjusts in real time based on each answer. The NWEA MAP uses adaptive testing. Each student's test is unique to their skill level.
Age Equivalent
A score expressing test performance in terms of the age group that typically achieves that score. A 7-year-old with an age equivalent of 10 performs like an average 10-year-old.
CogAT
Cognitive Abilities Test. A gifted screening test measuring verbal, quantitative, and nonverbal reasoning in grades K–12. One of the most widely used gifted assessments in the U.S. See CogAT Hub →
Composite Score
A single score combining multiple subtests or sections. The WISC-V Full Scale IQ is a composite of five index scores. Composites give a broad summary of overall ability.
Confidence Interval
A range around a test score indicating where the "true" score likely falls. A 95% confidence interval of 118–126 means we can be 95% confident the true ability falls in that range.
Fluid Reasoning
The ability to think logically and solve novel problems not previously encountered. Measured by WISC-V Fluid Reasoning Index and CogAT Nonverbal Battery. Less dependent on prior knowledge than crystallized intelligence.
Full Scale IQ (FSIQ)
The composite IQ score from WISC-V or WPPSI-IV. Mean of 100, SD of 15. Scores of 130+ (98th percentile) are classified as gifted or Very Superior. See WISC-V Hub →
Gifted and Talented (G&T)
A designation for students demonstrating exceptional cognitive abilities. Qualification criteria vary by district but typically require scoring at or above the 90th–98th percentile on a standardized ability test.
Grade Equivalent
A score expressing performance in terms of the grade level that typically achieves that score. A 3rd grader with a grade equivalent of 6.2 performs like the average student in the 2nd month of 6th grade.
Growth Percentile
A MAP metric comparing a student's score growth to similar students nationwide. A 50th percentile growth is exactly as expected. Used alongside achievement scores to assess progress.
ISEE
Independent School Entrance Exam. Used for admission to over 1,200 private and independent schools. Has four levels (Primary, Lower, Middle, Upper) for grades 2–12. See ISEE Hub →
IQ (Intelligence Quotient)
A score measuring cognitive ability relative to age peers. Modern IQ tests (WISC-V, WPPSI-IV) use a scale with mean 100 and standard deviation 15. "IQ" is shorthand for a Full Scale IQ score.
Lexile Level
A reading difficulty measure linked to MAP reading scores. A Lexile of 800L represents grade-level reading for most 4th graders. Used to match students with appropriately challenging books.
NAI (Naglieri Ability Index)
The NNAT's primary score. Mean 100, SD 15. Scores of 125+ (95th percentile) typically qualify for gifted programs. Named after Dr. Jack Naglieri, the test's creator.
National Percentile Rank (NPR)
Shows what percentage of same-age or same-grade students a child outperformed. A 90th percentile means scoring higher than 90% of the national comparison group.
NNAT
Naglieri Nonverbal Ability Test. A nonverbal gifted screening test using geometric shapes. No reading or language required. Widely used for English language learners. See NNAT Hub →
Nonverbal Reasoning
Problem-solving using visual patterns, shapes, and spatial relationships — no language required. Measured by the NNAT, CogAT Nonverbal Battery, and WISC-V Visual Spatial Index.
Normal Distribution
The bell curve. Most IQ and ability tests are designed so scores cluster around 100, with equal numbers above and below. About 68% of scores fall between 85–115; 95% fall between 70–130.
Percentile Rank
The percentage of students in a comparison group who scored at or below a given score. A 95th percentile means 95% scored lower. Different from percentage — a 95th percentile ≠ getting 95% correct.
Processing Speed
How quickly and accurately the brain processes simple information. Measured by the WISC-V Processing Speed Index. Students with slow processing may have strong reasoning ability that is masked on timed tests.
Raw Score
The number of correct answers before any conversion. Not meaningful on its own — raw scores are converted to scaled scores, standard scores, or percentile ranks for interpretation.
RIT Score
The MAP Test's score scale (roughly 100–300). RIT (Rasch UnIT) measures absolute skill level — the same RIT score means the same skill regardless of grade. See MAP Hub →
SAS (Standard Age Score)
The CogAT's primary composite score. Mean 100, SD 16. A score of 120–125+ (90th–95th percentile) typically qualifies for gifted programs. See CogAT Hub →
Scaled Score
A transformed score that adjusts for test difficulty across different forms and administrations. Allows fair comparison between students who took different versions of the same test.
Stanine
A 9-point normalized score scale dividing the normal distribution into bands. Stanines 1–3 are below average, 4–6 are average, 7–9 are above average. Used by OLSAT, ISEE, and many other tests.
Standard Deviation (SD)
A measure of how spread out scores are around the mean. Most IQ tests use SD=15. One SD above the mean (score of 115) = 84th percentile. Two SDs above (130) = 98th percentile (gifted range).
Standard Score
A score expressed in standard deviation units from the mean. Most cognitive tests use mean=100, SD=15. Standard scores allow comparison across different tests measuring similar abilities.
Subtest
A specific component task within a larger test. The WISC-V has 16 subtests grouped into 5 indexes. The CogAT has 9 subtests grouped into 3 batteries. Subtests reveal specific cognitive strengths and weaknesses.
Verbal Reasoning
The ability to think about and reason using words and language. Measured by the CogAT Verbal Battery, WISC-V Verbal Comprehension Index, and ISEE Verbal Reasoning section.
WISC-V
Wechsler Intelligence Scale for Children, Fifth Edition. The gold standard IQ test for children ages 6–16. Administered by a psychologist; produces an FSIQ and five composite index scores. See WISC-V Hub →
Working Memory
The ability to hold and mentally manipulate information in mind while performing a task. Measured by the WISC-V Working Memory Index. Essential for following multi-step instructions and mental math.
WPPSI-IV
Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition. An IQ test for children ages 2½–7½. Used for early gifted identification and developmental evaluation. See WPPSI Hub →