How do you account for external factors in an incrementality test?

To account for external factors in an incrementality test, several strategies can be employed:

Designing Control Groups: The control group in an incrementality test acts as a proxy for what would have happened to the treatment group in the absence of the marketing intervention. This helps in isolating the effect of external factors by ensuring that any observed differences between the control and treatment groups can be attributed to the marketing activity itself.

Carefully Choosing Testing Periods: When choosing a testing period, you should consider any seasonal factors and decide if you want to specifically test during or avoid unique seasonal moments. Some seasonal factors, like Black Friday, will affect the full population while others, like a hurricane, will only affect a certain subset of the population.

Use of Geo-Testing: Techniques like geo-testing can help in accounting for external factors by comparing performance across different regions or segments. This approach helps in understanding how external factors might differently impact various segments.

Regular Testing and Recalibration: Since external factors such as seasonality or the consumer economic climate can change over time, it is important to conduct incrementality tests regularly. This allows marketers to recalibrate their models and account for any changes in the external environment.

By employing these strategies, marketers can better isolate the impact of their marketing activities from external influences, leading to more accurate measurement of incremental effects.