# Trimmed Mean The trimmed mean is the average value of a series excluding the smallest and biggest points. Netdata applies linear interpolation on the last point, if the percentage requested to be excluded does not give a round number of points. The following percentile aliases are defined: - `trimmed-mean1` - `trimmed-mean2` - `trimmed-mean3` - `trimmed-mean5` - `trimmed-mean10` - `trimmed-mean15` - `trimmed-mean20` - `trimmed-mean25` The default `trimmed-mean` is an alias for `trimmed-mean5`. Any percentage may be requested using the `group_options` query parameter. ## how to use Use it in alarms like this: ``` alarm: my_alarm on: my_chart lookup: trimmed-mean5 -1m unaligned of my_dimension warn: $this > 1000 ``` `trimmed-mean` does not change the units. For example, if the chart units is `requests/sec`, the result will be again expressed in the same units. It can also be used in APIs and badges as `&group=trimmed-mean` in the URL and the additional parameter `group_options` may be used to request any percentage (e.g. `&group=trimmed-mean&group_options=29`). ## Examples Examining last 1 minute `successful` web server responses: -  -  -  -  ## References - .