Description: This article overviews control groups and explains how and why control groups are used in InnovidXP.


What is a control group?

A control group within the scientific field is a group separated from the rest of the experiment so that the independent variable being tested cannot influence the results. A similar approach is used in the InnovidXP platform, where control groups are used to estimate expected numbers in attribution and visitor rate.

How InnovidXP control groups work

The image below shows a spread of households. All the blue circles here are households that have been exposed to a brand’s TV advertising in the week that a spot airs or in the 30 days prior. All the remaining green circles have not been exposed and so are eligible to potentially be added to the control group. Control groups are created weekly for use at the spot level.

 

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How control groups are used

Attribution

The number of visits captured from the control group can tell us how many visits we should expect by chance following a spot of a given size. 

The difference between the actual number of visits and the expected number of visits forms the incremental attributed response. Daily control visit rates can vary due to seasonal and weekday patterns. For example, Black Friday would show different volumes when compared to an average day.


TV Influence

TV Influence is the difference between the exposed group and control group visitor rates. It is expressed as an uplift percentage and it is important to note that it uses visitor rates and not visit rates within the calculations.


Control Group Variations

There are variations within the control groups:

Regional control groups

These are filtered by the Market Area so when building control groups for regional campaigns, only households within Market Areas that were served impressions are eligible for the control group. The geographical representation of those impressions is matched.

OTT control groups (synthetic spots)

As there is no such thing as a single spot with multiple impressions for OTT, synthetic spots have to be created by grouping together impressions by day, publisher, and creative.

Hold-out groups

In certain workflows, the client can provide their own hold-out groups. These are more similar to a traditional scientific control group as they can be made up of households that are within the target audience but are not served the adverts.


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