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I dispute what you are saying, as someone who has studied that Lewis & Rao paper in detail. Advertising academia is pretty much just as mixed up as advertising
by mlthoughts2018 8y ago
I dispute what you are saying, as someone who has studied that Lewis & Rao paper in detail. Advertising academia is pretty much just as mixed up as advertising in practice.
Here is another paper worth reading on it [0] (which cites Lewis & Rao), but provides fairly clear evidence of a distribution of outcomes of digital ad campaigns with a lot of probability mass on the side of positive lift.
The place where issues come in via Lewis & Rao is on the side of poor statistical methodology, particularly in the calculation of necessary statistical power.
But those discussions are all stuck in bad frequentist estimation techniques, and in industry there are practitioners using Bayesian methods, for example such as Gelman’s proposed “type sign” and “type magnitude” errors, with well-calibrated priors that treat the possibility of negative lift seriously.
I strongly disagree with the idea that “ads don’t work” is an “open secret” like you say. Rather, “measuring ads is extremely complicated” is the known conclusion, and marketers are just coming around to the fact that you have to invest in extremely advanced statistical methods to even know if ads are working, let alone to optimize them for an audience, especially inclusive of things like audience privacy, opt-out policies, paychological well being and so on.
[0]: https://marketing.wharton.upenn.edu/wp-content/uploads/2017/08/Johnson-Garrett-PAPER-VERSION-2.pdf https://marketing.wharton.upenn.edu/wp-content/uploads/2017/...
- tomrod 8y agoThe open secret is that the incremental impact is small, not that it is non-existent. In experience, small enough to be questionable economically. The more interesting work has been showing where a consumer's offline transactions are impacted by online ads.
- mlthoughts2018 8y agoThe cited paper above, and even the influential 2018 Facebook paper by Gordon et al that tries to lobby for randomized controlled trials both disagree with your claim. The observed incremental lift on digital conversion outcomes (particularly account signups and purchases from an online shopping cart) is (median) somewhere around 8% - 17% based on close to 500 different very large field experiments. The distribution is skewed so that the ~30% standard deviation represents mostly outcomes higher and only somewhere between 9% and 22% showed negative lift (which, as the Facebook paper points out, can also be related to the difficulty of observational statistical methods used for post facto causal inference). 8% lift is quite significant. There’s no open secret of “small impact” at all. https://www.kellogg.northwestern.edu/faculty/gordon_b/files/fb_comparison.pdf https://www.kellogg.northwestern.edu/faculty/gordon_b/files/...