# standard deviation

> English word · Noun

## Definitions
1. A measure of how spread out data values are around the mean, defined as the square root of the variance. Represented with the Greek letter σ (sigma).

## Etymology
Coined by English mathematician, biometrician, and eugenicist Karl Pearson in 1894 in his paper "On the dissection of asymmetrical frequency curves".

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/standard-deviation