# Can I exclude outliers when calculating mean or standard deviation (small-sample)?

#### alexalexst1

##### New Member
Hey,
I am analyzing my results for a high-school biology paper. My data set consists of 20 groups in total, each having 4 repeats, so each is a small sample. I have a few (4) outliers that have a value lower than the control group (which is practically impossible and thus certainly the effect of a technical error).

Can I exclude the outliers when calculating the mean value or standard deviation, as they largely affect both parameters?

I am quite green when it comes to statistics, so I would hugely appreciate your help. Many thanks!

#### Miner

##### TS Contributor
If you know a specific reason for an outlier, such as it being a measurement error, data entry error, or non-representative sample, it is acceptable to remove the outlier. However, if the reason is unknown, it is unwise to remove the outlier. It is better to move to using robust statistics and tests.