Discrepancy in Google Analytics data when using segments

2
votes

I'm having a tough time with Google Analytics, trying to understand why the value of metrics changes when segments are applied.

There is a standard audience overview report, which is based on 100% of sessions (no sampling) and the view is not filtered. The period is March of 2017.

Standard "All visitors" segment looks like this:

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Then, there is another built-in segment called "Bounced Sessions". When I apply this segment, the "All visitors" values changes:

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Amount of users increases, but the count of pageviews decreases.

Any ideas how to explain this?.. Thank you in advance!

1
google-analytics

1 Answers

0
votes

Oki, there can be, multiple reasons. Let me explain first how these numbers are calculated, then we move on to your query.

There two types of data gathering and manipulation from google.

Pre-calculated data -- pre-aggregated tables

These are the precalculated data that Google uses to speed up the UI. Google does not specify when this is done but it can be at any point of the time. These are known as pre-aggregated tables

Data calculated on the fly

Some that you do which result in computation or manipulation falls under this category. Like using segments, creating custom reports etc.

Coming to your problem. When you apply segment, every metric that it effects will be calculated again. Thus it may result in numbers greater than you see in normal view.

Standard audience overview report is pre-aggregated at some point of the day. When you apply segment, the results will be calculated with the fresh data. Since latter is the latest, it will automatically give you increased number of the metrics. Even you can see a decrease as well, all depends on your data and user behavior.

Resolution: If you are a premium user, use Big Query. You must rely on big query for every metric as they are fresh and calculated on the fly