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Understanding the ideal GA4 audience scope for session and event criteria
Can someone help explain why I am encountering issues with choosing scope while creating an audience group in GA4? Let’s say that the membership duration is 30 days by default, and the condition is to include web users whose page path & query string (or any event with the page_url attribute) contains a certain string. Let’s talk about a user, John who had 2 sessions (A and B) that met the criteria on 5/6, 1 session (C) that met the criteria on 5/7, but 1 session (D) that didn’t on 5/8. Now depending on condition scope, the groups work differently.
So, why does the estimated audience size on GA4’s interface show as 1 < 3 < 4 = 2 in this scenario, whereas I had assumed it would be 1 < 2 = 3 = 4 based on the conditions? Any insight into this would be appreciated. Thanks for your time!
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2 Replies
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To understand this, you need to understand how GA4 calculates its audience size. The equation (1 < 3 < 4 = 2) signifies that the audience size varies based on the scope conditions in GA4 and it doesn't always correlate with the number of sessions that meet your criteria in a linear way.
The scope can be set at "User", "Session" or "Event". GA4 measures audience condition scope differently. For "User" scope, if any user session or event meets the criteria within 30 days, the user is included in the audience size. For "Session" scope, if any session meets the criteria in 30 days, it's counted in the audience size even if the same user had different sessions. For "Event" scope, GA4 counts each individual event that meets the criteria within 30 days.
If we take John's example, according to "User" scope (condition 1), John is counted as one user since he met the criteria within 30 days. In the "Session" scope (condition 3), John contributes three since he had three sessions that met the criteria. Using "Event" scope (condition 4), John contributes two, given if he only triggered two events that met the criteria, regardless of his sessions. Condition 2 wasn’t mentioned clearly in the question.
That's why the audience size could appear as you've witnessed (1 < 3 < 4 = 2). The number of sessions that meet the criteria doesn't always directly correspond with your audience size, as it also depends on the condition scope.
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In GA4, the estimated audience size depends not only on your specified conditions but also on the scope you select when creating the audience, which can be confusing as it is not always straightforward.
The scope determines how GA4 applies the conditions that you specified. If you set the scope to “user,” GA4 checks whether the condition was true for the user at any point during the membership duration. If you set the scope to “session,” GA4 only checks whether the condition was true during the individual sessions. A “session” scope would mean that if a session does not meet the condition, it (and the user) would be excluded from that audience, even if the user had other sessions that met the condition.
In your example, because the conditions are based on sessions, the number of audience members that GA4 estimates can vary greatly depending on the scope. This is why the estimated audience size shown as 1 < 3 < 4 = 2 in this scenario. This is due to the specifics of the GA4 algorithm and how it treats and classifies sessions/users for audience creation.
Therefore, it's not that there is necessarily a problem with your audience creation, but it's rather a difference in understanding how Google Analytics 4 creates audiences based on the scope and conditions you set.
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