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Random Assignment
“A well-run lottery can make groups comparable without knowing every factor that separates them.”
01 / SUMMARY
In short
Random assignment uses chance to decide who receives each condition. On average it balances known and unknown factors, although any particular sample can still be imbalanced.
03 / SCENE
In the wild
A generator assigns participants to two interface versions before their completion rates are measured.
04 / LIMIT
The limit
Random does not mean haphazard, and randomization does not fix attrition, poor measurement, or noncompliance.
FINAL NOTE
What remains
Distinguish random population sampling from random assignment to conditions.