---
title: "Stanine"
description: "A stanine is a standardised score on a nine-point scale with a mean of 5 and a standard deviation of 2. The name contracts 'standard nine'. Each stanine covers a fixed slice of the normal distribution, so it reports a person's position deliberately coarsely — in nine bands rather than a hundred percentile points."
canonical: https://www.assessall.com/guides/glossary/s/stanine
updated: 2026-09-22
source: AssessAll
---

# Stanine

_Also known as: Standard nine._

A stanine is a standardised score on a nine-point scale with a mean of 5 and a standard deviation of 2. The name contracts 'standard nine'. Each stanine covers a fixed slice of the normal distribution, so it reports a person's position deliberately coarsely — in nine bands rather than a hundred percentile points.

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## The fixed slices

Stanine 1 covers the bottom 4% of the distribution, then 7%, 12%, 17%, 20% for stanine 5 in the middle, then 17%, 12%, 7%, and 4% for stanine 9 at the top. The scale was developed by United States Army Air Forces psychologists during the Second World War, where a single-digit score was a practical advantage.

The coarseness is the design, not a limitation. Nine bands are close to what a typical instrument's measurement error can actually support, and reporting in stanines makes it awkward to claim a distinction between two candidates that the test cannot sustain.

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## Where it misleads

The bands are unequal in width, so a one-stanine difference means different things in different parts of the scale, and the boundaries are hard: a person a fraction of a point below a boundary is reported a whole stanine lower than someone a fraction above.

Report the underlying standard score alongside the stanine wherever a decision sits near a boundary, and never compute an average of stanines across scales.

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## How wide the band around a stanine actually is

The claim that nine bands are about as fine as measurement error will support is checkable rather than rhetorical. Because the stanine scale is defined with a standard deviation of 2, the standard error of measurement in stanine units is 2 × √(1 − reliability) — the general formula given in NCME’s instructional module on the topic as SEM = Sx√(1 − rxx′), where Sx is the standard deviation of the scores and rxx′ the reliability coefficient.

At a reliability of 0.85 that is 0.8 stanines, so a 95% confidence band around a reported stanine is roughly ±1.5 stanines — about three of the nine bands wide. A one-stanine gap between two candidates therefore sits well inside the error of either score, and reading it as a difference is reading noise.

Harvill states the reporting consequence plainly: "Score bands or confidence bands are the best way to report test scores to examinees or other interested persons." A stanine is already a coarse band; what it usually is not is a band whose width has been stated. Print the reliability next to it and the reader can work the width out in one line.

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Source: https://www.assessall.com/guides/glossary/s/stanine