How Optimizely Experimentation counts conversions

When sending a decision event to Optimizely Experimentation, how Optimizely assigns these events differs depending on which experimentation product you are using. User-level scope for visitor count and event scope for events in Web Experimentation, Optimizely Performance Edge, Feature Experimentation, and Full Stack (Legacy) assigns subsequent conversion events to the variation a user first encounters, depending on the date range.

In contrast, session-level scoping in Optimizely Personalization assigns conversion events to the last decision. It retains the session scope for events, making it suitable for behaviorally targeted campaigns with changing personalized experiences over time.

When segmenting on the Experimentation results page:

• The visitor count shows all visitors who had the attribute in their decision or had a conversion event with that attribute value.
• The conversions and events will only show events that have the attribute added to the event.

Example

While you are experimenting on your site's product detail pages, a user visits one of those pages, enters the experiment, is bucketed into a certain variation, and converts on an event you track: Click Add to Cart. The user converts a few times while navigating your site. Unless otherwise noted, assume that the user is shown the same variation in Sessions 1 and 3.

• E = Conversion events (also known as events) are triggered when a visitor converts to a desirable action, such as a click, page view, or purchase.
  • Conversion events in Optimizely Feature Experimentation.
  • Conversion events in Optimizely Web Experimentation.
  • Conversion events in Optimizely Personalization.
• D = Decision events (also known as impressions) special events fired when Optimizely Experimentation determines that a visitor is bucketed into a certain experiment or variation pair.
  • Decision events in Optimizely Feature Experimentation.
  • Decision events in Optimizely Web Experimentation.
• Session – A period of activity for a user.
  Optimizely Experimentation does not use sessions to assign data to decisions. Instead, sessions are used for illustrative purposes only. For example, Session 1 could be considered the user's activity on one day. Session 2 is the next day, and so on.

User-level scoping

When a user is shown a variation, subsequent conversion events from that user are assigned to that variation for as long as the experiment is running.

When a user encounters multiple variations for the same experiment, subsequent conversions are assigned to the first variation encountered within the date range of the results query meaning a user's conversions can be assigned to different variations, depending on the date range of your results query. For example, a user encountered Variation A at Time 1, then encountered Variation B at Time 2, and finally converted at Time 3. The conversion is assigned to Variation A if your results query spans from Time 1 to Time 3. If your results query spans from Time 2 to Time 3, the conversion is assigned to Variation B.

The following timeline shows how a single user's conversion events (E) are counted when results are scoped to the user.

Optimizely Web Experimentation counts 16 total conversion events (E) and assigns them to one user. This is a user-scoped event assignment. When the user is shown a variation, subsequent conversion events from that user are assigned to that variation.

• Users – 1
• Total conversion events scoped to the user – 16
• Unique converting users – 1

Session-level scoping

Session-level scoping in Optimizely Personalization assigns conversion events to the decision within that session while retaining the event-scope for events when segmenting, making it suitable for behaviorally targeting with changing personalized experiences over time.

When the user is shown a variation, subsequent conversion events (E) that are triggered are assigned to that variation. 

• experience_1 events – 3
• experience_1 unique converting events – 1
• experience_2 events – 2
• experience_2 unique converting events – 1