This is a question I couldn't quite explain to my boss' satisfaction.
I've made a data studio with GA4 that filters for certain blog pages. I used an individual metric to show the overall engagement rate for the pages (39%) and then a table that used page title as a break down dimension. She is confused because the engagement rates of the individual pages are between 22 and 35 so eyeballing it 39 doesn't seem like it could be the average. (I've checked and both entities have the same filter and time period set on them)
I said that you can't really average percentages and that it is likely that the denominator for the overall number is lower because sessions would only be counted once there but then counted on each of the pages. (lower denominator of users means a higher rate). This would depend on the engagement rate counting unique sessions but counting multiple engaged sessions? - like this:
I also said that regardless, it is the comparison of the trend over time and between the pages that is useful for analysis. But she would really like a stronger answer. Anyone else have a better idea?
Thank you very much.