Section 3 · OES Spec

Design and protocol

The intended experimental design — not just what happened to be measured.

This is the section where an open standard most improves trust. Tools usually preserve results, but rarely preserve the original design assumptions: the planned MDE, the multiple-testing policy, the peeking policy, the stopping rule. OES captures the protocol so future readers can judge how a result should be interpreted.

Fields

Field	Type	Purpose
design.type	enum	One of: ab, abn, multivariate, factorial, holdout, switchback, bandit, quasi_experiment.
design.randomizationUnit	string	user, account, session, device, pageview, region, etc.
design.analysisUnit	string	Unit used in metric analysis — may differ from the randomization unit.
design.assignmentMethod	string	Hashing, random draw, deterministic allocation, external assignment, etc.
design.hashAttribute	string	Attribute used for bucketing — e.g. user ID, anonymous ID, org ID.
design.hashSalt	string	Salt or namespace identifier, if exportable.
design.namespace	string	Layer/namespace used to avoid collisions with other experiments.
design.population	string	Eligible users, accounts, or events.
design.targetingRules	object[]	Inclusion rules.
design.exclusionRules	object[]	Exclusion rules — bots, internal users, specific countries or browsers.
design.trafficAllocation	number (0–1)	Total percent of eligible population included.
design.variantAllocation	object	Allocation per variant.
design.startDate	string (date-time)	Actual or planned start.
design.endDate	string (date-time)	Actual or planned end.
design.exposureDefinition	string	What counts as exposure.
design.triggerDefinition	string	What qualifies a user for analysis.
design.rampSchedule	object[]	Traffic ramp history.
design.concurrentExperiments	string[]	Known overlapping experiments.
design.interferenceRisk	object	Low / medium / high plus rationale.
design.power	number (0–1)	Planned power.
design.minimumDetectableEffect	number	MDE.
design.alpha	number (0–1)	Significance threshold.
design.multipleTestingPolicy	enum	none, bonferroni, fdr, hierarchical, metric_family, custom.
design.peekingPolicy	enum	fixed_horizon, sequential, always_valid, bayesian_monitoring, informal.
design.stoppingRule	string	Predefined rule for stopping or ramping.