# outlier

This page describes the metrics `outlier`

operator and how to use it in a metric query.

The metrics `outlier`

operator identifies metrics data points that are outside the range of expected values. Outliers help you spot unusual behavior in your metrics visualizations and track the behavior over time.

The `outlier`

operator tracks the moving average and standard deviation of a time series over a specified time window, and calculates a threshold band, outside of which data points are considered outliers. You can use optional qualifiers to specify the time window, the number of standard deviations beyond which a data point is considered an outlier, and the directionality of the deviation.

### outlier syntax

`metric query | outlier [window=<#>, threshold=<#>, direction=[ +- | + | - ]]`

Where:

`window`

is the time window, in minutes, over which to calculate the moving average and standard deviation of the time series. Default: 5m`threshold`

is the number of standard deviations from the moving average that defines the threshold band. Default: 3`direction`

specifies what deviation direction should trigger violations: positive deviations (+), negative deviations (-), or both (+-). Default: +-

In the visualization, the threshold band is the part shaded in pink. The outlier values are represented by the pink triangles.