How Amplitude computes conversions through funnels
Identify key differences between Funnel and Event Segmentation charts.
When you calculate conversion for a funnel in which users can complete the steps more than once, Amplitude buckets each user based on the values tied to the first occurrence of each event.
Understanding these implications is vital to drawing accurate conclusions from your analyses.
First-touch attribution scenarios
Assume you have a funnel that tracks registrations (complete registration) broken down by the landing page each user sees (view landing page). If you hold constant by session_id, users must complete both steps of the conversion process in the same session for Amplitude to count them as converted.
Scenario 1: Funnels using both Hold property constant and group conversions by
When a funnel analysis uses both the hold constant and broken down by functions, Amplitude bases conversion on the earliest entry within the session.
Consider the following events and conversion results as examples:
| Events | Conversion |
|---|---|
| A user sees Landing Page A and completes registration within the same session. | The session counts as converted, and Amplitude attributes the conversion to Landing Page A. |
| A user sees Landing Page A, then Landing Page B in the same session, but converts only after seeing Landing Page B. | Since that user saw Landing Page A first, Amplitude attributes the conversion within the session to Landing Page A. |
| A user sees Landing Page A, then Landing Page B in different sessions. | That user doesn't convert in the session where they saw Landing Page A. But that same user does convert in the session where they saw Landing Page B. Amplitude counts the Landing Page A session as not converted, and the Landing Page B session as converted. |
When you hold constant by session ID, your chart displays the number of user sessions that included a conversion, and not the number of users who converted.
Scenario 2: Funnels using group conversions by, but not Hold property constant
When only the broken down by function applies, Amplitude bases conversion on the earliest entry within the lookback window.
Amplitude groups users by the first landing page they saw within the lookback window (how they entered the funnel). Amplitude considers them converted if they trigger the final event within the duration of the conversion window.
For example, consider the following events and related conversions:
| Events | Conversion |
|---|---|
| A user sees Landing Page A and completes registration within the conversion window. | That user counts as converted, and Amplitude attributes the conversion to Landing Page A. |
| A user sees Landing Page A, then Landing Page B, and completes registration within the window for Landing Page A. | That user counts as converted, and Amplitude attributes the conversion to Landing Page A, since they saw that one first. |
| A user sees Landing Page A, then Landing Page B, but doesn't convert. | That user counts as not converted. The events negatively affect Landing Page A's performance, but don't count against Landing Page B. |
Amplitude calculates conversions broken down by a filter differently than a group-by. A group-by looks for the earliest and most complete conversion first, and then groups by the specified property value. A filter-by first accounts for the property you filter by before looking for a conversion.
The logic of unique user counts in funnel analyses
When counting by unique users, the baseline conditions for conversion are:
- A user must qualify for inclusion in the funnel: Amplitude can't filter the user out through the user segmentation panel. Any filters set in the Segment by module only apply at the time the user triggered the first funnel event.
- A user must enter the funnel and complete all steps in the conversion window: The user must enter the funnel and complete all steps within the stated conversion window to count as converted in the final funnel step. Otherwise, Amplitude counts the user based on how far they progressed through the funnel.
When Amplitude counts by uniques, it only counts the earliest and longest conversion for each unique user:
- Longest: In this context, longest means the most complete conversion—the completion of the most required steps within the funnel.
If Amplitude finds multiple conversions that meet the longest definition, it selects the first one and counts that as when conversion occurred.
- Earliest: Amplitude measures earliest using the first converting sequence chronologically, if more than one exists.
When you use the broken down by function, Amplitude continues to use the longest/earliest logic to bucket users according to the property that was present at their point of funnel entry.
If you use Hold constant by in your analysis, Amplitude looks for the longest/earliest converting sequence within the same user session. When it does, the unit of measurement changes to unique user and session ID pairings.
When counting by event totals, the earliest/longest logic doesn't apply. Instead, Amplitude considers all conversion paths taken or attempted, rather than just the earliest/longest path per user. Amplitude then attributes the paths to the property for the event in the step it was broken down by.
Funnels versus event segmentation
The Funnel and Event Segmentation charts provide different types of analyses, and can display different results. The following table highlights some of those differences:
| Funnel | Event Segmentation |
|---|---|
| Shows steps a user takes to gauge experience | Shows what events users are triggering |
| Filters only apply to the first step | Filters apply to every event |
| User must execute step 1 to enter funnel | No funnel to enter |
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