# StuDded issue, StdDev, unknown

**URL:** <https://forum.inductiveautomation.com/t/studded-issue-stddev-unknown/14562>\
**Category:** Ignition\
**Created:** [June 20, 2017, 1:57am UTC](https://forum.inductiveautomation.com/t/studded-issue-stddev-unknown/14562 "2017-06-20T01:57:27Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Jhahn](https://avatars.discourse-cdn.com/v4/letter/j/8edcca/32.png) [@Jhahn](https://forum.inductiveautomation.com/u/Jhahn)\
**Post date:** [June 20, 2017, 1:57am UTC](https://forum.inductiveautomation.com/t/studded-issue-stddev-unknown/14562/1 "2017-06-20T01:57:27Z")

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When I try and use StdDev like in the example from the docs, I get an error thatthat stdDev is u known,/ does not exist…  
What am I doing wrong

stdDev({Root Container.Table.data}, “Weight”)

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [June 20, 2017, 2:09am UTC](https://forum.inductiveautomation.com/t/studded-issue-stddev-unknown/14562/2 "2017-06-20T02:09:31Z")

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Where are you trying to use it? This is an expression function that can only be used in a property binding, not in any scripts.

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<div class="post-metadata">

**Author:** ![Jhahn](https://avatars.discourse-cdn.com/v4/letter/j/8edcca/32.png) [@Jhahn](https://forum.inductiveautomation.com/u/Jhahn)\
**Post date:** [June 20, 2017, 2:29am UTC](https://forum.inductiveautomation.com/t/studded-issue-stddev-unknown/14562/3 "2017-06-20T02:29:58Z")

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ahh I was trying to use it on a button click. That must be it. That was driving me crazy thanks