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description: Geographic blocks versus individuals How to block/stratify
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# Real-world assignment & inference

See [geographic-segmentation-blocked-randomization](splits-randomization/geographic-segmentation-blocked-randomization "mention") for a mainly theoretical discussion of this

[facebook-split-testing-etc](splits-randomization/facebook-split-testing-etc "mention") for how to do split testing on Facebook, and the limits to traditional design given their setup
