# What is Standard Deviation and Percent Standard Deviation?

|If you’re in an advanced chemistry or college chemistry course you’re probably going to be asked to calculate the standard deviation of your results for a lab. It’s called a lot of things, but most usually either standard deviation or relative standard deviation. Here’s how to calculate it:

[Calculation]

SD or RSD = the square root of ((sum of (mean or average – value) / number of values – 1)

Then some professors or TAs will ask for the percent standard deviation or the percent relative standard deviation. The way to calculate the percent standard deviation is:

[Calculation]

Standard Deviation Value / mean or average value x 100

Hope this helps clear things up.

[Image Credit] Chad Miller

9 Comments

What a great resource!

Thanks for

your sharing, it’s very useful

A+ would read again

Good dispatch and this post helped me alot in my college assignement. Thanks you on your information.

Hi, I was searching through the website looking for some data and arrived by your weblog. I am amazed by the info that you’ve on this site. It displays how properly you comprehend this subject. Saved this net page, should come back again for long term. You, my pal, ROCK!!!

thanks for information

Hi,

The formula given above to calculate standard deviation is:

“SD or RSD = the square root of ((sum of (mean or average – value) / number of values – 1)”.

As far as I know, this formula is wrong, since the “average – value” values should be squared before being summed.

Thanks

Gaby

You saved my day and my report data

Thank you so much 🙂

Glad to hear that!