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A contextual bandit produced a high-single-digit conversion lift for one population

aws.amazon.com by Chidi Prince John 13 min read Editor score 7/10

In a seven-week online A/B test, Amazon Payments reports a high-single-digit relative lift in final-funnel conversion for one population and no improvement for another. The result and the finding that content, not the model, was the issue offer practical lessons for applied ML experimentation.

What
A multi-objective contextual bandit personalizes a product acquisition funnel by selecting content based on signals about each visit.
How
UCB selects content using estimated reward plus an uncertainty bonus, balancing exploitation with continued exploration.
Why it matters
Bandits can keep learning as new content variants arrive without waiting for a test to conclude, which suits the growing volume of generative-AI options.

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