Facebook Auto-Bidding Question (4)
Hi.
This is my first time with Facebook Ads and there's something I cannot understand about bidding.
I bid CPM and I generally prefer to let FB bid automatically for me. I also try to always create only 1 single ad per ad set because I remember @zeno explaining that this makes split testing more accurate since otherwise Facebook will favor whichever ad it wants based on some complex and usually meaningless criteria for performance.
So this screenshot here shows some of the different ad sets I split tested with only 1 ad per ad set. In all these ad sets, everything (audience targeting, device targeting, bidding, budget, text & headlines..) is exactly the same except from the images which are what I'm split testing.
What I don't understand here is why the average CPM for each ad set is different since everything except from the images is exactly the same? I see that CPMs can vary even between €0.90 and €1.74, which I marked with red to highlight it.
If I follow Facebook's logic, it feels like throwing a dice... If bidding is so random, I can just pick an ad with a good CTR and create several copies of it and try to find which one of them gets the best CTR and CPM combination but I guess it could be more complicated than that. Truth is, I didn't throw a lot of money on these ads and maybe after running for a longer time the bids would automatically adjust to similar values but this is just one of the many assumptions I could make, so I prefer asking STM instead.
Does anyone have an explanation on why this happens?
Facebook decides after very low level of significances. So when your ad has a good start because people click on it, facebook already decided the cpc for it.
That is why i would run several ad sets investigating the same thing. also, i would do 3 ads exactly the same under one ad set.
Originally Posted by Chunk
Facebook is a complex platform.
The thing is, you haven't run these long enough at all to get uniform impression distribution and CPMs, and even then they will vary because your ad performance + oCPM optimisation is going to be altering the audiences that are receiving the ad impressions.
You should focus more on scaling what works and giving Facebook conversion data to aid optimisation of the audience, otherwise bid CPC.
If you look at the first ad and second underlined ad, you can see you actually have similar eCPC's. The ad with higher CTR has higher CPM costs, which seems unusual at first, but consider that the higher CTR might be because the ad is being delivered in an earlier ad spot that has naturally higher CPMs, or is now being delivered to a slightly more expensive audience that is also more likely to click.
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