When you conduct a downward analysis, mixing dimensions and metrics of different scopes is not problematic in GA4 reports. It is problematic when you conduct upward analysis or mix dimensions of different scopes.
You can go down in the hierarchy from users > sessions > events but not upwards when mixing dimensions and metrics of different scopes in GA4 reports.
The hierarchy of scopes in GA4 can be visualized as:
1) User (highest level)2) Session3) Event (lowest level)
This hierarchy reflects the way data is structured and collected in GA4.
Downward Analysis:
>> You can mix user-scoped dimensions with session or event-scoped metrics.
>> You can mix session-scoped dimensions with event-scoped metrics.
This is because lower-level entities (events, sessions) always belong to higher-level entities (users).
Upward Analysis:
>> You should not directly attribute event-scoped dimensions to session or user-scoped metrics.
>> You should not directly attribute session-scoped dimensions to user-scoped metrics.
This is because higher-level entities can contain multiple lower-level entities, making direct attribution problematic.
For example, an event (e.g., page_view) is not tied to a single user in a one-to-one manner. It belongs to many users.
Similarly, a session can contain multiple events, so there is no single “Session” value to apply at the event level.
Mixing Dimensions of Different Scopes.
You should avoid mixing dimensions of different scopes as it could result in inaccurate data.
The downward and upward analysis rule does not apply when mixing dimensions of different scopes because dimensions don’t behave like metrics.
For example, The ‘First User Default Channel Group’ dimension has a ‘user’ scope. The ‘source/medium’ dimension has the ‘event’ scope.
Combining these two dimensions with different scopes creates a mismatch in the detail level they represent, resulting in inaccurate data.
“Do not mix dimensions and metrics of different scopes” is a simplified guideline to help marketers and analysts avoid creating incorrect reports.
But when mixing scopes is not avoidable, remember the upward and downward analysis approach.
