Web Experiment event tracking

Web Experiment uses impression events for analysis and billing. The Web Experiment script tracks impression events through the integration. Experiment analysis requires impression event tracking.

Impression events

The impression event is the same as the Feature Experiment exposure event, but has a different event type: [Experiment] Impression. Event properties contain the flag key and the variant of the flag or experiment that the user encountered.

When Amplitude ingests an impression event, Amplitude uses the flag key and variant to set or unset user properties on the user associated with the event. Setting user properties is essential for experiment analysis queries on primary and secondary success metrics.

Impression transformation

Web Experiment sends impression events in one form, and Amplitude transforms them into Amplitude-standard impressions upon ingestion. Amplitude modifies the event type and event properties for consistency with other Amplitude properties. Amplitude sets or unsets experiment user properties for accurate experiment analysis. If you're tracking impressions through a 3rd party customer data platform (CDP), the CDP records the event in its pre-transformation state.

Estimate monthly impressions

Amplitude tracks one impression event per experiment when Web Experiment applies a variant action to a page. To estimate the number of impressions per month, consider:

1. M = Your volume of monthly tracked users (MTU).
2. E = The number of experiments you run per month.
3. P = The average number of page views per user, per month.

Impressions Estimate = M * E * P

This estimate provides an upper bound. Target specific pages and audiences, or roll out to a subset of users to reduce the total number of impressions.