---
title: Standard Deviation (SD)
description: "This is probably the most quoted measure of dispersion and it's just the square root of the variance of a set of data. See [Variance: introduction](https://www.psyctc.org/psyctc/glossary2/variance/) and, for the details, [Variance: computation and bias](https://www.psyctc.org/psyctc/glossary2/variance-2/) (and perhaps [Square root](https://www.psyctc.org/psyctc/glossary2/square-root/)). #### Try…"
url: "https://www.psyctc.org/psyctc/glossary2/standard-deviation-sd/"
updated: "2024-08-16"
category: All OM book glossary entries
---

# Standard Deviation (SD)

This is probably the most quoted measure of dispersion and it's just the square root of the variance of a set of data. See [Variance: introduction](https://www.psyctc.org/psyctc/glossary2/variance/) and, for the details, [Variance: computation and bias](https://www.psyctc.org/psyctc/glossary2/variance-2/) (and perhaps [Square root](https://www.psyctc.org/psyctc/glossary2/square-root/)).

#### Try also

[Variance: introduction](https://www.psyctc.org/psyctc/glossary2/variance/)
[Variance: computation and bias](https://www.psyctc.org/psyctc/glossary2/variance-2/)
[Square root](https://www.psyctc.org/psyctc/glossary2/square-root/)

#### Chapters

Dispersion underpins pretty much all statistical methods so SD is implicit in Chapter 5.

#### Online resources

My shiny app [that gives you a confidence interval (CI) around an observed standard deviation](https://shiny.psyctc.org/apps/CISD/)

#### Dates

First created 14.iii.24, replacing an earlier even more minimal entry, links updated 16.viii.24.