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diff --git a/web/api/queries/stddev/README.md b/web/api/queries/stddev/README.md deleted file mode 100644 index 3f751a6e1..000000000 --- a/web/api/queries/stddev/README.md +++ /dev/null @@ -1,97 +0,0 @@ -<!-- -title: "standard deviation (`stddev`)" -sidebar_label: "standard deviation (`stddev`)" -custom_edit_url: https://github.com/netdata/netdata/edit/master/web/api/queries/stddev/README.md -learn_status: "Published" -learn_topic_type: "References" -learn_rel_path: "Developers/Web/Api/Queries" ---> - -# standard deviation (`stddev`) - -The standard deviation is a measure that is used to quantify the amount of variation or dispersion -of a set of data values. - -A low standard deviation indicates that the data points tend to be close to the mean (also called the -expected value) of the set, while a high standard deviation indicates that the data points are spread -out over a wider range of values. - -## how to use - -Use it in alerts like this: - -``` - alarm: my_alert - on: my_chart -lookup: stddev -1m unaligned of my_dimension - warn: $this > 1000 -``` - -`stdev` does not change the units. For example, if the chart units is `requests/sec`, the standard -deviation will be again expressed in the same units. - -It can also be used in APIs and badges as `&group=stddev` in the URL. - -## Examples - -Examining last 1 minute `successful` web server responses: - --  --  --  --  - -## References - -Check <https://en.wikipedia.org/wiki/Standard_deviation>. - ---- - -# Coefficient of variation (`cv`) - -> This query is also available as `rsd`. - -The coefficient of variation (`cv`), also known as relative standard deviation (`rsd`), -is a standardized measure of dispersion of a probability distribution or frequency distribution. - -It is defined as the ratio of the **standard deviation** to the **mean**. - -In simple terms, it gives the percentage of change. So, if the average value of a metric is 1000 -and its standard deviation is 100 (meaning that it variates from 900 to 1100), then `cv` is 10%. - -This is an easy way to check the % variation, without using absolute values. - -For example, you may trigger an alert if your web server requests/sec `cv` is above 20 (`%`) -over the last minute. So if your web server was serving 1000 reqs/sec over the last minute, -it will trigger the alert if had spikes below 800/sec or above 1200/sec. - -## how to use - -Use it in alerts like this: - -``` - alarm: my_alert - on: my_chart -lookup: cv -1m unaligned of my_dimension - units: % - warn: $this > 20 -``` - -The units reported by `cv` is always `%`. - -It can also be used in APIs and badges as `&group=cv` in the URL. - -## Examples - -Examining last 1 minute `successful` web server responses: - --  --  --  --  - -## References - -Check <https://en.wikipedia.org/wiki/Coefficient_of_variation>. - - |