The hidden problem behind campaigns that look profitable
When I entered the world of digital advertising, I was drawn to the balance between logic and creativity. I wanted to build campaigns that not only look great, but can prove, with data, that they generate real results.
Over time, I noticed that most professionals in the industry rely heavily on platform metrics — ROAS, clicks, conversions — without asking the essential question:
“What would have happened if we didn’t run the ad?”
This seemingly simple question separates a campaign that only appears to perform from one that truly creates value.
The answer lies in a fundamental concept for any performance-oriented specialist: incrementality.
What incrementality really is
Incrementality represents the difference between the results generated by an advertising campaign and the results that would have occurred without that campaign. It measures the true impact of advertising — not just what platforms attribute by default.
In simple terms, an effective campaign is not the one that brings in the highest volume of sales, but the one that generates additional sales — sales that would not have happened without advertising. This is the difference between a caused conversion and an attributed one.
For example, if a customer would have purchased anyway, even without seeing the ad, that sale is not incremental. But if someone decides to buy only because they were exposed to your message, that conversion represents the direct impact of your campaign.
The basic formula for calculating incremental lift is:
Incremental lift (%) = (Test group result – Control group result) / Control group result × 100*
If your test group (people who saw your ads) generates 125 conversions, and your control group (people who didn’t) generates 100, the incremental lift is:
(125 – 100) / 100 × 100 = 25%
This tells us the ad drove a real 25% increase above the natural baseline.
How to measure incremental impact
To correctly evaluate the impact of a campaign, you need to compare two similar groups of users:
The performance difference between these two groups shows your incremental lift.
But for this difference to matter, it must be statistically significant.
1. Incrementality testing
This method relies on causal inference. It allows you to verify the direct effect of advertising by building a controlled experiment that isolates whether ad exposure actually changes user behavior.
2. Statistical significance
A difference between the test and control group can sometimes happen by chance.
To rule this out, we use a T-test, which compares the averages of the two groups and estimates the probability that the difference is random.
If the p-value is below 0.05, the result is considered statistically significant — meaning there is at least a 95% chance the effect is real.
3. Confidence interval
Every estimate carries uncertainty. A confidence interval shows how confident we can be about the result.
For example:
4. Multiple linear regression
In the real world, not everything can be controlled. Seasonality, discounts, parallel channels, or even the day of the week can affect results.
To isolate the true impact of advertising, we use multiple linear regression (OLS). This model evaluates how each variable contributes to the final outcome, giving you a clearer view of the real role advertising plays.
Why ROAS alone isn’t enough
Advertising platforms attribute conversions according to their own algorithms.
A customer who would have purchased anyway — but happened to see an ad somewhere in the journey — is often counted as an “ad-driven conversion.”
This leads to misleading conclusions: campaigns that look profitable but do not actually create new value.
Without an incremental framework, these attribution distortions can lead to poor budget and strategic decisions.
And when causality is missing, companies often:
The result? Inefficient investment based on appearances, not evidence.
Why incrementality matters for your business
Incrementality is the foundation of a marketing strategy built on real results.
It allows you to determine precisely which part of your sales is caused by advertising and which would have occurred naturally.
This distinction is essential for:
Only by understanding incremental impact can you accurately evaluate the return on your advertising investment.
In essence, incrementality transforms advertising from an art of intuition into a science of causality.
How to apply incrementality in your campaigns
You don’t have to be a statistician to apply these principles — you only need to adopt an evidence-based mindset.
At DAFE.RO, we build performance strategies grounded in data, using incremental testing, statistical analysis, and advanced attribution models.
The goal is simple: identify which campaigns truly drive growth and eliminate the spend that brings no value.
If you want to understand the real impact of your ads and learn how to scale only the campaigns with positive incremental lift, write to me at hello@adelamincea.ro or fill out the contact form.
In short
Incrementality is not just a math formula — it’s a shift in perspective.
It forces you to move:
In our industry, everyone talks about performance — but the real difference is made by those who can prove, with data, that their advertising creates real value.
Because what you cannot prove, you cannot optimize.
And what you cannot optimize, you cannot scale.
