Attribution · The holdout · Element
The design
What is withheld, from whom, for how long.
The part
What it is
Geographic holdouts are the most practical: withhold in comparable regions and compare against matched ones.
Duration has to exceed the sales cycle, or the test measures the pipeline rather than the demand.
The smallest level
The attributes it carries
Each attribute is one of the framework’s shared types. What a date is, and how it is written, is defined once for the whole model — the note here says what it means in this particular place.