Bucketing
How a testing tool assigns each visitor to a variant and keeps them there on later visits.
Also called assignment
Bucketing turns a visitor's ID into a variant, usually with a hash so the same visitor always lands in the same bucket. Consistent assignment matters: a shopper who sees the control on Monday and the variant on Tuesday muddies both.
Good bucketing is random with respect to anything that affects the result, and gives each variant its planned share of traffic.
A visitor who saw the variant's new size guide on their first visit sees it again when they come back two days later to buy.
Related terms
- Traffic allocationHow much of the eligible traffic enters a test, and how it is divided between the variants.
- Sample ratio mismatch (SRM)When the number of visitors in each variant differs from the planned split by more than chance can explain: a sign the test is broken.
- Server-side testingRunning experiments in your own server or edge code rather than by changing the page in the visitor's browser.