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+<!--
+title: "Trimmed Mean"
+sidebar_label: "Trimmed Mean"
+description: "Use trimmed-mean in API queries and health entities to find the average value from a sample, eliminating any unwanted spikes in the returned metrics."
+custom_edit_url: https://github.com/netdata/netdata/edit/master/web/api/queries/trimmed_mean/README.md
+learn_status: "Published"
+learn_topic_type: "References"
+learn_rel_path: "Developers/Web/Api/Queries"
+-->
+
+# 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 alerts like this:
+
+```
+ alarm: my_alert
+    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:
+
+-   ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=min&after=-60&label=min)
+-   ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=average&after=-60&label=average)
+-   ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=trimmed-mean5&after=-60&label=trimmed-mean5&value_color=orange)
+-   ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=max&after=-60&label=max)
+
+## References
+
+-   <https://en.wikipedia.org/wiki/Truncated_mean>.