# Arithmetic mean

**Arithmetic mean [əˈrɪθ.mə.tɪk miːn]: **the most commonly known mean.

To get the arithmetic mean you add the values of all observations and then divide by the number of observations. In most cases this is what we mean, when we colloquially talk about the average.

Other means are: the median or the truncated mean. Which one you should chose depends on the kind of data in front of you.

The main differnce lies in the way these means are affected by extreme values – their so called robustness against anomalies. The arithmetic mean is not very robust, because it is influenced by every single value – even the extreme ones.

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