We are facing a very worrying issue regarding to Google Analytics. We developing a software in .NET framework, which is able to query Google Analytics servers by using HttpRequests (through measurement protocol).
The issue is that we find inconsistency when we query the same historical data.
Let me share with you two example query, which can presentate it:
and End-date parameters are the SAME for both queries. ONLY the Start-date parameter differ, and there is NO FILTERs defined.
Query1 date range:
Query2 date range:
By these two queries for example the following row's session count has to be the same but these are not.
In the Google Analytics API JSON response we can see that this Custom Segment contains huge amount of data, and the queries using sampling.
Example sample size
Query1 sample size: 509968
Query2 sample size: 813574
So my question would be how can the session count in february 2015 differ, if the only difference between the two query is the start-date parameter?
Could it be the sampling, that cause the data discrepancy?
Could it be one of the property or settings of the Custom Segment?
Do you have any idea what could cause this mathematically?
If not, I am afraid this is a bug, and I'd like to report it to the Google Analytics developer team, please share a direct contact with me if you can.
Thank you, Regards,