What is Incrementality?
Incrementality, also known as causality, is the measure of lift. Incremental lift answers the question of how many people would have converted (eg, purchased) in the absence of seeing the ad.
How is it measured?
To determine true incremental lift, an audience is segmented to create a holdout or control group and receives no advertising. The other half of the group does receive advertising and the conversion rates are compared. However, there are still factors involved that make it difficult to get accurate conversion rates such as (1) Of the advertised group, it is hard to verify that everyone saw the ad (2) Those who saw the ad might already be brand loyalists (3) there is still data bias because of the competition for those consumers. Also, to measure lift, multiple tests need to be run to ensure correct measurement.
Why is incrementality testing important?
If incrementality testing is done correctly, it can determine the effectiveness of your marketing campaigns and if an ad truly influenced conversions.