# Standard deviation as a percentage

#### jolodo

##### New Member
Hi i'm new here and have a really quick question,
How do you interpret a standard deviation given as a percentage (in this case 20%)?
I need to use the variance in further calculations (working out type i and ii errors), the data is normally distributed, and the sample size is 30, i have further information but i'm not sure its relevant.
I'm sure the way to proceed is simple, but i'm stuck!!
Any help would be apreciated

#### ledzep

##### Point Mass at Zero
You sure it was standard deviations? It is quite likely that you're given the Coefficient of Variation (CV) , which are reported as percentages.

$$CV= \frac{\sigma}{\mu}$$ where $$\sigma$$ is your standard deviation and $$\mu$$ is your mean.

#### jolodo

##### New Member
That would make more sense!! But I just checked and it definitely means standard deviation: "with population standard deviation 20%.”
Could it mean that the standard deviation is 0.2*(sample size) = 0.2*(30)? That was my first guess at what to try but I’m not sure there is any mathematical justification!!

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#### chippy

##### New Member
Just to make sure, your data isn't percentages as well?

#### ledzep

##### Point Mass at Zero
Could it mean that the standard deviation is 0.2*(sample size) = 0.2*(30)?