Would they have
bought anyway?

Incrementality testing estimates the effect of a marketing intervention by comparing outcomes with what would likely have happened without that change. Dema uses geo-based experiments, with treatment and control regions and a pre-test period to inform the comparison.

A holdout can investigate what existing spend contributes. A new-channel test can investigate additional demand. Scaling tests can explore what happens when you increase or decrease spend. The test design should follow the question and the decision you need to make.

The comparison needs to account for the regions, their pre-test behavior and the experiment design. Raw sales totals alone are not a causal result. Read the estimated effect with its uncertainty, diagnostics and the conditions under which the experiment ran.

Dema supports gross sales, net sales, net gross profit, new-customer profit, returning-customer profit and new-customer count. These are different ways of reading the same experiment: a channel can increase sales without producing the contribution or new customers you expected.

Allow enough time for the intervention and for delayed outcomes to arrive. The duration depends on volume, expected effect and the design. Dema includes treatment and post-treatment windows; review statistical power and the appropriate timing before launching.

An inconclusive result does not establish that a channel has no effect. The data may not distinguish the effect from noise at the precision the decision needs. Review the interval, test power and execution before deciding whether to repeat, redesign or use other evidence.

Finalized test evidence can inform MMM calibration and the factors used for causal attribution. The scope matters: a result from one channel, market and spend level should be interpreted in that context when it informs a wider decision.