Google Analytics Data inconsistency

[GoogleCodeExporter]

Hi,

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:

ProfileId, 
Metrics(ga:sessions), 
Dimensions(ga:year, ga:month), 
the CustomSegment, 
Start-index, 
Max-result, 
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:
start-date: 2014.10.27
end-date: 2015.08.20

Query2 date range:
start-date: 2014.01.01
end-date: 2015.08.20

By these two queries for example the following row's session count has to be 
the same but these are not.

Query1 result:
ga:year: 2015
ga:month: 02
ga:sessions: 52979

Query2 result:
ga:year: 2015
ga:month: 02
ga:sessions: 58289

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?

Ive also tried  https://ga-dev-tools.appspot.com/query-explorer/ with 
HIGHER_PRECISION to sampling but the result is the same. This is huge amount of 
data though, if the sample size is almost a million. 

If there is no mathematic answer for this, I am afraid this is a bug, and 
please share a direct contact with me if you can.

Thank you, Regards,
Daniel Farkas

Original issue reported on code.google.com by farkasda...@gmail.com on 14 Sep 2015 at 8:15

[GoogleCodeExporter]

Please contact me, if you have any clue what could be the root cause of this 
issue.

Original comment by farkasda...@gmail.com on 1 Feb 2016 at 6:14

[GoogleCodeExporter]

Sampling.
Attempt to request a significantly smaller date range: 
https://developers.google.com/analytics/devguides/reporting/core/v3/reference#sa
mpling

The best place to ask questions about using and developing with Google 
Analytics APIs, libraries, and SDKs is on Stack Overflow. Make sure and use one 
of the following tags:

google-analytics — for general questions about Google Analytics.
google-analytics-api — for questions specific to one of the Google Analytics 
APIs.

Original comment by mcoh...@google.com on 1 Feb 2016 at 6:44

• Changed state: Invalid