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Facebook A/B Testing Guide: How to Avoid 10 Common Mistakes

Facebook A/B Testing Guide: How to Avoid 10 Common Mistakes

A/B testing Facebook Ads belongs to the top practices used by digital marketers today. It's widely applied, and almost anyone can assume that they've already mastered the art of split testing. Nevertheless, even experienced managers can sometimes commit mistakes that result in lost budget and nerves. This article will show you how to avoid the common errors when launching A/B tests and get the most out of them.

A/B testing, otherwise called split testing, is the technique that can help define the types of Facebook ads that work best for their audience. Using them, you can determine which ad headlines, body copy, images, CTAs, or combinations of these bring the most result. Besides, it's possible to experiment with the kinds of the audience and types of placements.

Split testing is so helpful because it lets marketers change their variables and figure out what works best. It's also the perspective tool that'll help create money-making marketing campaigns in the future.

During testing, users are divided into several groups and shown different variations of a specific variable. Depending on ad peculiarity, a marketer may decide to test one of the following variable groups:

  • Creative — includes text, images, videos, and other creative types.
  • Placements — Facebook platforms where your ads can appear (Instagram, Messenger, Facebook, Audience Network)
  • Delivery Optimization — the ability to allow Facebook to optimize the budget for the campaigns that work best.
  • Audience — the kind of audience that best reacts to the ads. It can be filtered through demographic, geographical location, and psychographics.
  • Product Set — the groups of items in your catalog.

How to a/b test facebook ads?

To set up the A/B testing, you need to open Facebook Ads Manager and go through a sequence of easy steps:

  1. Select a campaign objective

  2. Name your campaign and turn on the “Create A/B Test” button. The message will show that your current campaign will be the A version of your testing. Once you launch it, you’ll be offered to edit its duplicated version.

  3. Set up the campaign, ad sets, and ads according to the elements you want to split test and the desired budget.

  4. Once you are done, click "Publish". You'll see the "Create A/B Test" pop-up. It's where you'll set up the actual test. To proceed, click the "Get Started" button.

  5. Select whether you want to make a copy of the current ad or pick another existing ad and click "Next".

  6. You'll have to choose the variables you want to test in the next stage. You can select among testing:

    • Creative
    • Audience
    • Placement
    • Custom

  7. The "Review and Publish" window is the last step in creating your A/B test. Here you have to give your test a name and select the metric by which the winner will be determined. Lastly, choose the starting and ending date of your testing.

    Selecting the "End test early if the winner is found" option would allow you to save funds if Facebook determines the clear winner before the test end date.

  8. Click the "Duplicate Ad Set" button once you are ready to start testing.

Common mistakes

One must follow several distinct rules to make the Facebook split testing results statistically relevant and applicable across multiple campaigns. We've prepared the set of most common mistakes you may encounter and their solutions.

Mistake 1

Having an unrealistic hypothesis

How to do it right

A hypothesis is a specific, real question that the split test can answer. It can become unrealistic if you pick a question for it randomly, without regard for the objective of your campaign.

For instance, when you see that pricing page is one of the most visted on your site, you can formulate your hypothesis in the following way:

If we place prices for our product on the creative, this will positively impact CTR.

It’s an example of a realistic hypothesis, the effectiveness of which can be proven by the test results. The less realistic version could be the following:

Changing the background color on the creative will impact CTR.

Just because we think some people might like green over yellow.

Mistake 2

Testing several variables simultaneously

How to do it right

It may look perspectively to test several variables at the time, but the reality is quite the opposite. Having a single variable per test will help you evaluate test results more effectively.

Mistake 3

Testing it for too short or too long

How to do it right

Depending on the specificity of your campaign, Facebook suggests running it for not least then 7 days and not more than 30 days. If you run the campaign for too short or too long, you may receive incomplete results, which equals the waste of your resources.

Mistake 4

Using the wrong Facebook Campaign Structure

How to do it right

When testing diverse in-ad elements, you can structure your ad campaigns either by putting all your ad variations into a single ad set or by placing each variation into separate ad sets. However, when you choose the first variant, Facebook starts to auto-optimize your ads so that you can't receive relevant results. Thus, the better option is to select the second type of structure.

Mistake 5

Not making sure that you’ve received valid results

How to do it right

There is a golden rule:

To ensure that your test results are valid, you need to get at least 100 conversions per each ad variation.

Mistake 6

Setting the inadequate budget

How to do it right

You need to be precise when estimating your budget. So, to know which numbers are optimal, you have to multiply your cost-per-conversion by the number of ad variations per 100. For instance:

3$ (cost-per-conversion) * 3 (number of variations) * 100 = 900$ (you estimated budget)

Note: if one of the ad variants significantly exceeds the others, you can close the test after receiving fewer conversions. However, getting at least 50 conversions per variation is still recommended.

Mistake 7

Avoiding prioritization of your Facebook Ad tests

How to do it right

Always keep in mind that your testing capacity is not limitless. Thus, think about the ad elements that could have the highest effect on your ads. Prioritize them and test the most influential first.

For instance, it would be much more helpful to test variations for CTA buttons (such as “Try for free” or “Start trial”) before testing the color of a cat on your banner.

Mistake 8

Choosing the wrong audience

How to do it right

Facebook suggests that your audience is large enough to support your research needs. When choosing your audience for the first time, you can decide to either pick it similarly to your existing customer base or invest in two large sample audiences to get an insight into who are your potential customers.

Mistake 9

Starting A/B testing too late

How to do it right

A/B testing is a powerful tool that can help you optimize your campaigns and get the most out of them. And so, by conducting them early on the MVP stage, you’ll ensure yourself better return chances and open the opportunity to optimize the campaigns over and over again.

Mistake 10

Stopping on a single A/B test

How to do it right

Conducting A/B tests offers you valuable insights. These should prompt you for further testing to receive even better results. Testing is not a one-time action but a process that should be overdone.

Feedback to your creative team

Creating an ad involves multiple professionals, including marketers, designers, copywriters, and targetologists. To make their work productive, one has to set their communication correctly.

Besides, it's crucial to provide all the specialists with timely feedback — the element that is ignored too often. This mistake is critical, and its impacts can hardly be fixed by receiving good A/B testing results.

To make the communication process easier across teams, one can use various marketing tools.

With AdBraze, you can make the interaction inside your team more effective by using Task manager. By boosting the communication between departments, it makes interaction more effective and productive. It provides visibility of all processes inside the team and makes all the staff aware of the ad settings that work best. It also provides an easy way for designers to see which creatives perform better.


A/B testing, or split testing, is a powerful tool to boost ad performance. It’s also the most common practice in digital marketing today. Nevertheless, this technique can also be misused and so bring extra expenditures to the marketers.

Now that you’re aware of the 10 most common mistakes and the ways to tackle them, we hope you can use A/B testing to its full potential.

And remember never to stop on the achieved results but to keep testing, as this is the key to highest performance.

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