How experimentation and incrementality testing reveal the true value of marketing

A version of this article was previously published by Forbes.

When you are marketing a product, a successful advertising campaign is only half the battle. Without marketing experimentation, its true value is hard to prove. The true test comes when you meet with the CFO. For a C-suite leader, marketing metrics like clicks and impressions are a means to an end. What they look for are provable business results that drive revenue.

This disconnect with what is most important for a business exposes the core flaw of traditional, “last-click” thinking. If you only look at the last touchpoint prior to purchase, you are missing the full power of your user’s journeys, and your attribution model misses the full context of what is possible.

This is why we analyze the full customer path — from first exposure to final conversion — to create a more accurate and actionable marketing mix model (MMM). It’s the vehicle taking us from fragmented vanity metrics to holistic data-driven decisions.

John Joba, head of marketing data science at Rocket Mortgage, has witnessed firsthand how this approach transformed the dynamic between his team and the finance department. “We moved from reactive justification to proactive planning,” he says. “We have a common language with finance firmly grounded in business value first.”

Core to creating that common language is incrementality testing, a critical form of marketing experimentation. It reframes advertising from a required cost to a growth engine for value that allows a business like Rocket to level up its media planning strategy and marketing and business outcomes.

A new era of access to incrementality testing

Incrementality testing is a known quantity, but it’s been expensive and labor-intensive until recently. Running a single experiment could have cost upward of $100,000, making the research viable only to the largest enterprises.

Small-to-medium businesses had to rely on less sophisticated, which meant that marketers couldn’t tell whether an outcome was due to their own efforts or an organic side effect.

To ensure more advertisers have access to these critical tools, in 2025 Google Ads lowered the cost of an incrementality experiment from a previous high of $100,000 to a minimum of $5,000. This significant reduction democratized the tool, extending its benefits to a broader user base for new types of analysis.

Verify your impact on campaign performance

With incrementality testing now widely available, businesses can expand where and how they experiment to understand where to put their next investment and how to refine their MMMs. Here are three common testing examples that can directly inform and improve your campaign strategy.

1. You’re running an ad campaign on YouTube to drive new brand searches and conversions. There’s been a nice bump for both, but you need to prove your team’s work led to performance gains. By comparing results between shoppers who saw your ad and those who were eligible to see it but didn’t, you can pinpoint which decision led to the biggest difference. This allows you to properly assign credit and understand how valuable YouTube is to your overall strategy.

2. The same goes for paid search campaigns. You (and your CFO) won’t have to wonder whether a spike in attention came from your ad placement or organically occurring interest. Through incrementality testing, you can determine who responded to the search spend versus who sought out your brand directly, so you reach net-new customers instead of feeding on your own traffic.

3. Similarly, when you’re launching a new product, you want to bring in fresh revenue instead of drawing dollars away from the products you already have. Incrementality testing can shed light on these situations as well, helping to distinguish new customers from regulars redirecting their purchases.

In all of these use cases, the ability to trace cause and effect provides a clearer view of a business’s financial operations, at any size. We’re leaving behind the era of “we think” to “we know.” This confidence can then become the foundation for marketing. And, for a perfect illustration of how much can be gained through testing, we can turn to Rocket Mortgage.

How Rocket Mortgage used testing to unlock insights and growth

Rocket Mortgage used Google Ads to test a demand generation campaign, revealing an insight that would have otherwise gone unnoticed. Testing proved that the marketing team’s campaign drove the desired outcome but also generated 23% more value than their model had originally estimated. From this single, clearly defined learning, they recalibrated their entire MMM. Instead of just upping their spending, the team used these insights to refine for more accurate modeling, which brought a higher degree of certainty to the entire investment strategy.

“We can confidently invest in brand building, knowing that we can demonstrate its contribution to the bottom line,” Joba says. “And perhaps, most importantly, we’re empowered to make bold moves, like our full brand restage, because we have a measurement system that we trust.”

A critical component of ad measurement best practices

The closer a marketing team can get to certainty about their effectiveness, the better positioned they’ll be for success. That’s why incrementality testing is evolving into a fundamental part of an effective media planning strategy, allowing marketing to shift its perception of being a cost center to a proven driver of growth.