Skip to main content

Documentation Index

Fetch the complete documentation index at: https://docs.siftstack.com/llms.txt

Use this file to discover all available pages before exploring further.

​
Overview

This guide walks you through the process of building Rules with dynamic thresholds using Sift Family statistics. To go beyond fixed Rule thresholds, use Family statistics in Rules to automatically flag when a new test Run deviates from your historical baseline. The Rule evaluates against aggregated values computed from your entire Family of reference Runs, such as the mean ± 3 standard deviations. This is particularly useful for hardware testing workflows where acceptable signal behavior varies across tests but should stay within the statistical envelope of known good Runs.

​
Prerequisites

  • A Family with at least two included members. See Creating Families.
  • At least one Family statistic configured on the Family. See Configure Family statistics.
  • Permission to create Rules in your organization (Admin or Editor).

​
Create a Rule with a Family statistic aggregate

To create a Rule with a Family statistic aggregate:
  1. In Sift, click the Rules tab and click New Rule, or click Create Rule from the Family overview page (which prepopulates the Family).
  2. Choose one or more Assets to which the Rule applies.
  3. In Input Channels, toggle Aggregate Comparison.
  4. Configure the Family statistic aggregate using the steps below.

​
Select an aggregate input

In Aggregate Source, seect the Family whose statistics you want to use as the threshold.

​
Select statistics

Select one or more statistics from the Family as the Aggregate Channel Group Input. When you select multiple statistics, the T-0 alignment and dynamic window option show the union of all available configurations across the selected statistics. Common multi-statistic patterns:
  • Select both an avg and stdev statistic to build a sigma-band Rule.
  • Select min and max statistics to flag exceedances of the Family envelope.

​
Set T-0 alignment

From the T-0 Alignment dropdown, choose the alignment configuration defined within the Family. This determines how the Run under test is time-synchronized with the Family aggregate for comparison.

​
Set the data range

Optionally select a dynamic window: a time range anchored around the T-0 alignment that bounds the data used in the computation. By default, the full Run range is used. If the window you need doesn’t exist yet, you can create it here without leaving the Rule editor.

​
Write the Rule expression

Reference your Family statistic inputs using the variable placeholders assigned in the editor. For example, $A for the mean stat, $B for the standard deviation stat.

​
Sigma band example

To flag when a channel falls outside the Family mean ± 2 standard deviations: 
($1 < ($A - 2 * $B)) || ($1 > ($A + 2 * $B))
Where $A is the avg statistic, $B is the stdev statistic, and $1 is the channel under test. This checks both the lower and upper bounds of the sigma band.

​
Envelope example

To flag when a channel falls outside the Family min/max envelope: 
$1 < $A || $1 > $B
Where $A and $B are Family statistic references for the minimum and maximum aggregates.

​
Preview the Rule

Choose a Run to evaluate the Rule against a specific Run before saving:
  1. In Rule Preview, click Select Run to select a sample Run.
Sift prompts you to resolve the alignment for the selected Run: map the Run’s available alignment configurations to the Family’s T-0 alignment so the comparison is time-synchronized correctly. Sift evaluates the Rule and plots the result in the preview chart. The Family statistic time series is displayed as a reference overlay alongside the Run’s channel data, in relative time aligned to T-0. Annotations are shown on the chart where the Rule condition is met.

​
Save and activate the Rule

To save the Rule:
  1. Once the preview looks correct, click Save.
Rules containing aggregate channel inputs cannot be set to evaluate live.

​
View results in reports

To run a Family Rule against a Run and view results in a report:
  1. Create a report template that includes the Family Rule, or open an existing one.
  2. Generate a report from a Run, either from the Run detail page or the Reports section. Sift prompts you to resolve alignments for the Run, just as in the Rule Preview flow.
  3. Map the Run’s alignment configurations to the Family’s T-0 alignment before the report generates.
The generated report shows:
  • The alignment configuration used for the Run under test.
  • A relative-time chart with the Family statistic overlay and the Run’s channel data.
  • Annotations at the correct relative time positions, with absolute timestamps available in the Annotation detail.

​
Reference Rule dependencies from a Family

To see which Rules reference a given Family or Family statistic:
  1. In Sift, click the Families tab.
  2. Click the name of the Family to open its overview page.
  3. Click the Rule references tab. This lists all Rules that depend on stats from this Family, grouped by statistic.
Use this list before modifying or deleting a statistic to understand downstream impact.