I see this problem in every organization, and it’s (usually) not intentional. Nor is it is a miscalculation.
Facebook has at least 2 different ways of measuring ‘Average Duration of Videos Viewed’.
1. sum(total seconds viewed) / sum(total users viewed)
This is the calculation the C-suite thought they were reporting.
2. If sum(total seconds viewed) > 3
Then ( sum(total seconds viewed) / sum(total videos viewed) )
This is the calculation they were reporting.
The end result?
Calculation 2 greatly inflates ‘Average Duration of Videos Viewed’ for a couple different reasons.
So it’s an error, right?
Maybe. But I doubt it.
In reality, Facebook probably has a perfectly valid use for both metrics. And they probably use both for a variety of functions.
Calc 2 makes sense if we want to know how long did users actually ‘watch’ a video. Because who can watch a video in under 3 seconds? And lots of videos autoplay as you scroll through a page — so are those being counted if the user isn’t viewing it?
Calc 1 makes sense if we want to look at aggregate platform usage per user.
Is one of them wrong?
No, they each have a place in the business.
The Real problem
The first rule of data analysis is #knowyourdata
Management at Facebook doesn’t know their data well enough to recognize:
- there are 2 separate calculations for ‘Average Duration of Videos Viewed’, or
- which calculation to use when
Always take due diligence to understand what a metric means and when to use it. Don’t assume anything. Especially when communicating it to the outside world or using it to make decisions. So pretty much always.
Big ad buyers and marketers are upset with Facebook Inc. after learning the tech giant vastly overestimated average viewing time for video ads on its platform for two years, according to people familiar with the situation.
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