The Power of Multi-Armed Bandit Tests for Marketers

Simbar Dube

Simbar Dube

Simba Dube is the Growth Marketing Manager at Invesp. He is passionate about marketing strategy, digital marketing, content marketing, and customer experience optimization.
Reading Time: 5 minutes

Are you looking to take your conversion game up a notch? If so, you’re not the only one! 

We’ve all been there, hoping to turn clicks into conversions and website visitors into loyal customers. But regular optimization methods don’t always cut it. That’s where Multi-Armed Bandit (MAB) tests come into the picture. Think of them as your secret weapon, ready to help you hit those conversion bullseyes.

This article covers what exactly MAB testing is, how it differs from the regular A/B tests, and what makes them suitable for you. We’ll also uncover some methods that make it easy to help you run MAB tests. Let’s start! 

Understanding Multi-Armed Bandit Tests and How it Differ from A/B Testing 

A multi-armed bandit test is an experimental method that involves testing multiple options (like different versions of an ad or webpage) to identify which option performs best for a specific goal, such as getting more clicks or purchases. 

Unlike traditional A/B testing, where all options are tested equally, multi-armed bandit tests allocate more resources to the options that show promise as the test progresses, leading to more efficient and adaptive decision-making.

Let’s understand the multi-armed bandit test with an example and contrast it with the good old A/B testing. 

How do multi-armed bandit tests differ from traditional A/B testing?

Setting up traditional A/B tests entails splitting your audience into two groups: Group A sees Version A (the current version), and Group B sees Version B (the new version). 

You measure which version performs better based on a single metric – it could be click-through rates or purchases. However, this approach has limitations and can lead to missed opportunities.

Multi-Armed Bandit (MAB) tests take a smarter and more adaptive approach. 

Imagine you’re a marketing manager optimizing the design of an email template. You have five different subject lines to test. In an A/B test, you’d randomly send each subject line to a portion of your audience and pick the one that got the highest open rate.

Here’s where MAB tests shine. Instead of sticking to just one subject line during the whole test, MAB tests adapt and learn as they go. 

Initially, MAB tests try out all five subject lines on a smaller scale. As data comes in, the test starts to favor the subject lines that show better results early on in the experiment. This is called “exploitation” – focusing on what seems to work best so far.

However, MAB tests are also exploratory. They don’t put all their eggs in one basket right away. They continue to explore the other subject lines to see if any of them might perform better. 
This balance between exploration and exploitation means you’re not just locked into one option before the test ends.

Multi-Armed Bandit Tests
Image Source: Conductrics

Benefits of Multi-Armed Bandit Tests

1. Efficient resource utilization 

Traditional A/B tests divide your audience evenly between different variations. This often leads to a slower learning process and allocating valuable traffic to less effective options. 

MAB tests help overcome this downside. They dynamically allocate more traffic to promising variations as they emerge, making better use of your limited resources. This adaptive approach ensures that your audience is exposed to the most effective options more frequently, leading to faster learning and optimization.

2. Faster and adaptive decision-making 

MAB tests adapt to changing trends and user behavior in real-time. Unlike traditional A/B tests, where you might need to wait until the end of the test to identify a winner, MAB tests start optimizing as soon as they detect patterns of performance. 

This helps you make quick and informed decisions based on emerging data, leading to more efficient campaign optimization.

3. Improved conversion rates

The primary goal of any marketing optimization effort is to improve key metrics like click-through rates, conversions, and revenue. 

MAB tests are designed to maximize these metrics by directing traffic toward the variations that show the best possible results. This leads to a higher likelihood of identifying the best-performing option and achieving higher conversion rates in a shorter timeframe.

4. Balancing Exploration and Exploitation 

Running MAB tests is all about balancing exploration and exploitation. 

While the major focus is on directing traffic to variations performing the best, MAB tests continue to explore other options as well. 

This helps you avoid jumping the gun on a choice that might not be the best fit early on. Instead, it keeps the door open for ongoing learning, like discovering those unexpected gems that could really make a difference down the road. 

5. Flexibility in Testing Goals 

MAB tests can be adapted to various testing goals, such as optimizing email subject lines, website layouts, ad designs, or pricing strategies. 

The dynamic nature of MAB tests allows them to be applied across different marketing channels and scenarios, providing a versatile solution for optimizing a wide range of marketing elements.

6. Continuous Learning and Improvement 

Integrating MAB tests into your marketing strategy establishes a culture of continuous learning and improvement. 

Regularly running MAB tests helps you stay ahead of changing trends and user preferences, ensuring that your marketing efforts remain relevant and effective.

How Will You Run Multi-Armed Bandit Tests? 

You can design and run a bandit test in many different ways. 

One of the most common approaches is the Epsilon-greedy method. Here’s how it works: 

Epsilon-greedy method

The Epsilon-Greedy strategy is one of the most straightforward approaches to running MAB testing. It’s also a go-to way to balance exploring new options and exploiting the best-performing ones. 

Let’s dive deeper into the Epsilon-Greedy strategy.

The Epsilon-Greedy strategy gets its name from two components: “epsilon” and “greedy.” 

  • Epsilon represents the exploration factor (this is 20% part of the method).
  • Greedy signifies the exploitation factor (this takes 80% part of the entire process). 

It’s all about balancing trying new things (exploration) and sticking with what’s already working (exploitation).

Here’s how it works: 

Epsilon-greedy method
Source: CXL

Let’s take an example. 

Suppose you’re conducting an email subject line test with four variations: A, B, C, and D. You choose an epsilon value of 0.2 (20% exploration, 80% exploitation).

  • In 20% of cases, the strategy selects a variation at random to explore, regardless of its past performance. This could be variation B.
  • In the remaining 80% of cases, the strategy chooses the variation that has performed best so far. If variation A has the highest open rate, it will receive most of the traffic.

Aside from the Epsilon-greedy algorithm, there are other methods you can use to run MAB tests. 

For example, you could also use: 

  • Thompson Sampling Strategy: This entails using probability distributions to guide variation selection. It’s like picking options based on their “winning probabilities.”
  • Upper Confidence Bound (UCB) Strategy: The UCB strategy balances well-performing testing variations with those that have yet to be explored.
  • Successive Elimination Strategy: With this strategy, you’ll begin by testing all variations and gradually eliminate the less effective ones. The main focus will remain on the best-performing options.

Conclusion: Unleashing Optimization Potential with Multi-Armed Bandit Tests

Traditionally, A/B tests have been the go-to options for many optimization experts. 

However, A/B tests have limitations, and MAB tests help you recover. For one, they adapt in real-time, allocating resources to the variations that show the best results while keeping an eye on the unexplored. Think of having a personal coach who guides you toward the most suitable choices without missing out on potential gems.

MAB tests also ensure limited resources are invested where they matter most. The strategies we’ve covered, including the most prominent one, the Epsilon-Greedy approach, will help you run these tests without much hassle. 

Remember, it’s not just about cracking the conversion code; it’s about constantly fine-tuning, experimenting, and finding those hidden gems that skyrocket your success.

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Simbar Dube

Simbar Dube

Simba Dube is the Growth Marketing Manager at Invesp. He is passionate about marketing strategy, digital marketing, content marketing, and customer experience optimization.

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