How does excel calculate the site average values in the generic behaviour report page?
(i.e. average site bounce rate, %exit, time on page etc.)
The values I get in my manual Excel calculations of average values (using downloaded GA data) are different to the ones provided in the GA report.
Specifically the mean value I calculate for my bounce rate in Excel is 17.84% but Google Analytics tells me it's 53.10%
How can those numbers be so different?
The total number of pageviews for the site over the past month is ~ 7,400 so it's not a huge sample size, but it wouldn't seem to explain that sample size. Is Google doing some other kind of average, or silently filtering outliers?
Detailed Recreation added below
- Set Google Analytics to a month.
- Navigate to the Behaviour tab > Site content > All pages
- Set sessions to all sessions
Google Analytics Average
The Google Analytics Average I'm using is the top of the bounce rate column on the main landing page. (Screenshot to identify it below.)
On the Google Analytics behaviour sheet I selected the maximum number of rows (Shown at the bottom of the report) and then exported it as an XLSX spreadsheet.
I got the excel mean average by using the AVERAGE formula on the bounce rate column. (Sum all the bounce rates and then divide by the total number)