The biggest hurdle is rarely statistics. It is that the organisation changes too many things at the same time. Geo tests require discipline, a clear intervention, stability in other efforts, and a comparable control group. To make it work you need: - A decision forum that can freeze certain changes during the test - Clear rules for agencies and internal teams on what can be optimized - Consistent data collection and shared definitions As attribution weakens, geo tests become a robust way to build decision confidence, but only if the organisation respects the test.