Incrementality

Measured as

Measure Incrementality with a fixed attribution window, conversion event, and spend basis before comparing campaigns or creative tests.

Misused when

• Treating attribution as causal truth (it's model-based credit).
• Running tests without clean holdouts (contamination breaks results).

Operator takeaway

• Use holdouts or geo-experiments to estimate incremental lift.
• Be careful with short tests when purchase cycles are long.
• Use Incrementality only inside a stable attribution rule, conversion definition, and time window so campaign comparisons stay honest.
• If performance changes, check whether the metric moved for a real business reason or because the measurement setup changed underneath you.

Next decision

• Quantify the impact with Incrementality Lift Calculator if you need to turn the definition into an operating assumption.
• Read Incrementality: how to tell if ads are actually driving growth if the decision depends on interpretation, policy, or trade-offs beyond the raw formula.