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Analytics number of events changes according to time frame (using filters)

[ Edited ]
Visitor ✭ ✭ ✭
# 1
Visitor ✭ ✭ ✭

Hello,

 

I'm having issues understanding what happens when I'm querying my Analytics data. To elaborate my queries, I'm using the Query Explorer.

 

Hereby what I want:

  • Metric: Total events, filtered by Event label
  • Dimensions: per isoWeek per year

I noticed that I get different results when I change the start date of my analysis.

 

This not normal I think, what happened on week 16 in 2016 should not change if the total time frame I'm studying starts on week 1 2015 or week 1 2016… Or do I understand something wrong?

 

Hereby some screenshots that will show you the results obtained, changing only the start date of the analysis.

 

Start-date 01/2016:

Screenshot 2016-08-25 10.55.21.png

 

Start-date 01/2015:

 

 Screenshot 2016-08-25 10.55.28.png

 

I do not have this issue when I'm not using filters and only using Total Events. Is there a problem with Analytics' filters, or something that I do not understand about dimensions?

 

Thanks a lot for your help,

RB

 

[EDIT: I have also tried directly on the custom reports from GA, and I have the same problem: the values obtained of the weeks are changing when I extend the time frame to previous data also… Even when I use only one dimension: isoYearIsoWeek. It makes no sense…]

1 Expert replyverified_user

Re: Analytics number of events changes according to time frame (using filters)

Top Contributor
# 2
Top Contributor
Hi,

What you're seeing is data sampling. It means that Google Analytics estimates the metric based on a random subset of full data. So for a different date range a different sample data is used hence the different results.
Sampling is applied when more than 500000 sessions occurred in the date range you're viewing. Please check the Google Analytics help document below about sampling:
https://support.google.com/analytics/answer/2637192?hl=en

Also check this article for examples:
https://megalytic.com/blog/understanding-google-analytics-data-sampling

Hope this helps.

Arnold Majlath, Google Analytics Top Contributor
Circle Me On Google+ | Visit me @ Redfly Digital

Re: Analytics number of events changes according to time frame (using filters)

Visitor ✭ ✭ ✭
# 3
Visitor ✭ ✭ ✭
Hi,

Thank you for your answer. I understand the issue, and why the problem occurs only when I increase too much the time frame.
However, the change is quite a lot here, are you sure it is the only reason? (The increase is 21%…)

Thanks again, RB
Marked as Best Answer.
Solution
Accepted by topic author Raphael b
August 2016

Re: Analytics number of events changes according to time frame (using filters)

Top Contributor
# 4
Top Contributor
Hi,

The difference can be quite big, it is different for each metric. Please check the article below, it has a comparison between sampled and unsampled data.

http://www.blastam.com/blog/can-you-trust-your-google-analytics-data

Arnold Majlath, Google Analytics Top Contributor
Circle Me On Google+ | Visit me @ Redfly Digital