Whether it works · The control · Element
The holdout
Who sees the non-personalised version.
The part
What it is
A random sample, consistently assigned so the same people stay in the control and the comparison holds over time.
Small enough that the cost is acceptable and large enough that the comparison is readable.
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.