[I’ve tweeted about this before.]
If fashion stores believed in A/B testing, they would probably only sell white XXL shirts. Most customers would fit tent-sized garments; most colours go well with white. Giant colourless shirts would presumably have the better sales conversion rate by far.
But of course this would be far from optimal.
Customers come in different shapes and sizes. If you really want to maximise conversion, you will have to tailor to their specific needs and personal preferences. A/B testing might be the latest fashion, but the truth is that some customers will have a taste for B even though the majority might fancy A. This is why these 20 lines of code will beat A/B testing every time.
The trick is not to figure out whether A is better than B, but when A is better than B; and for whom.
Marketing should not be one-size-fits-all.