Participating Units
Understand how Statsig counts participating units in an experiment, including exposure rules, deduplication, and how to interpret unit counts in results.
What are participating units
In Statsig, Participating Units (sometimes referred to as participating users) are a subset of an experiment's total exposed unit count relevant to a particular metric. Participating Units are the units with a non-zero denominator value for metric types that require a numerator and denominator value. Statsig uses these units in statistical calculations for ratio-based metrics.
Statsig computes ratio metrics only for users that have a non-zero value in the denominator. The user must have triggered the denominator event on a given day for Statsig to include them in the daily ratio. Statsig excludes users that don't trigger the denominator event during an experiment from the test vs. control comparison of a ratio metric.
Example
An example of this type of metric for an e-commerce company could be "Total Items Purchased per Order", measuring the average basket size. The numerator would be the count of total items bought, and the denominator would be the total number of orders submitted. If an experiment were run on the checkout flow, Statsig would include only users who had at least one Order event in the "Total Items Purchased per Order" ratio metric.
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