# How to define error

**URL:** https://discourse.pumas.ai/t/how-to-define-error/82
**Category:** How-to
**Created:** [November 19, 2019, 5:55am UTC](https://discourse.pumas.ai/t/how-to-define-error/82 "2019-11-19T05:55:36Z")
**Posts on this page:** 1
**Showing post:** 18

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### Author: ![sai\_matcha](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/sai_matcha/32/297_2.png) [@sai\_matcha](https://discourse.pumas.ai/u/sai_matcha)
#### Post date: [March 5, 2020, 7:06am UTC](https://discourse.pumas.ai/t/how-to-define-error/82/18 "2020-03-05T07:06:39Z")

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Hi @andreasnoack  
dv ~ @. Normal(cp, sqrt(cp^2\*σ\_prop)) this is error defined in workshop examples ([https://tutorials.pumas.ai/html/exercises/workshop\_solutions.html](https://tutorials.pumas.ai/html/exercises/workshop_solutions.html))

which one equivalent to that Normal(cp, cp_σ) or Normal(cp, cp_sqrt(σ²)) ??

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