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Multi arm bandit

Quick answer

A multi-arm bandit is a statistical method used in marketing for testing multiple strategies, offers, or options concurrently to determine which one performs best. Similar to A/B testing, but instead of splitting the audience evenly among all options, a multi-arm bandit test dynamically adjusts the traffic allocation to each option based on their ongoing performance.

Key takeaways

  • Multi arm bandit gives teams shared language for experiment planning and analysis.
  • It should be tied to a clear metric, audience, behavior, or decision whenever possible.
  • Consistent definitions make optimization work easier to compare across tests.

Definition

A multi-arm bandit is a statistical method used in marketing for testing multiple strategies, offers, or options concurrently to determine which one performs best. Similar to A/B testing, but instead of splitting the audience evenly among all options, a multi-arm bandit test dynamically adjusts the traffic allocation to each option based on their ongoing performance. It's named after a casino slot machine, where each "arm" is a different strategy or option and the "bandit" is the unpredictable reward.

What Multi arm bandit means in A/B testing

In A/B testing, Multi arm bandit gives teams a clearer way to describe user behavior, measurement, or decision-making. It is most useful when connected to a primary metric, a specific audience, and the decision the experiment is meant to inform.

Why Multi arm bandit matters

Multi arm bandit matters because measurement terms shape how teams judge experiment outcomes. When the definition is clear, marketers and analysts can connect the result to a real user behavior, metric, or business decision instead of relying on vague performance claims.

Example of Multi arm bandit

For example, a growth team may test a new landing-page message and use Multi arm bandit to understand whether the change affected the intended behavior. The term helps turn a test result into a specific next step instead of a generic statement that the page performed better or worse.

How to use Multi arm bandit

Use Multi arm bandit as part of your experiment documentation. Define the metric or behavior it refers to, choose where it fits in the funnel, and use the same definition when comparing results across tests.

Common mistake

A common mistake is using Multi arm bandit as a vague label instead of tying it to a measurable behavior or decision. If different teammates mean different things by the same term, experiment planning and result interpretation become less reliable.

Related A/B testing terms

FAQ

What does multi arm bandit mean in A/B testing?

A multi-arm bandit is a statistical method used in marketing for testing multiple strategies, offers, or options concurrently to determine which one performs best. Similar to A/B testing, but instead of splitting the audience evenly among all options, a multi-arm bandit test dynamically adjusts the traffic allocation to each option based on their ongoing performance.

Why does multi arm bandit matter for experiments?

Multi arm bandit matters because measurement terms shape how teams judge experiment outcomes. When the definition is clear, marketers and analysts can connect the result to a real user behavior, metric, or business decision instead of relying on vague performance claims.

How should teams use multi arm bandit in an experiment?

Use Multi arm bandit as part of your experiment documentation. Define the metric or behavior it refers to, choose where it fits in the funnel, and use the same definition when comparing results across tests.

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