Treatment/control contamination

advertising

In a geo-lift experiment, cells assigned to control can still receive treatment exposure via platform audience expansion, ad-adjacent delivery, or a resident's movement into a treatment cell, biasing the measured lift toward null.

Detection

Non-zero measured impression/exposure delivery within cells designated as control.

Mitigation

Use a geographic buffer/no-man's-land between treatment and control cells to absorb spillover
Independently verify zero-delivery in control via platform reporting or third-party exposure logs, not assumption

Affected conversions

Admin polygons → H3 (weighted crosswalk) weighted
Cell system → cell system approximate