> **Deprecated**: This endpoint will be removed in a future version. Use the `updateExperimentFields` and `saveAndStartNewIteration` instructions on [Update experiment](https://launchdarkly.com/docs/api/experiments/patch-experiment) instead.
Create an experiment iteration.
Experiment iterations let you record experiments in individual blocks of time. Initially, iterations are created with a status of `not_started` and appear in the `draftIteration` field of an experiment. To start or stop an iteration, [update the experiment](https://launchdarkly.com/docs/api/experiments/patch-experiment) with the `startIteration` or `stopIteration` instruction.
To learn more, read [Start experiment iterations](https://launchdarkly.com/docs/home/experimentation/create#start-an-experiment-iteration).
Request
This endpoint expects an object.
hypothesisstringRequired
The expected outcome of this experiment
metricslist of objectsRequired
Details on the metrics for this experiment
treatmentslist of objectsRequired
Details on the variations you are testing in the experiment. You establish these variations in feature flags, and then reuse them in experiments.
flagsmap from strings to objectsRequired
Details on the feature flag and targeting rules for this iteration
canReshuffleTrafficbooleanOptional
Whether to allow the experiment to reassign traffic to different variations when you increase or decrease the traffic in your experiment audience (true) or keep all traffic assigned to its initial variation (false). Defaults to true.
primarySingleMetricKeystringOptional
The key of the primary metric for this experiment. Either primarySingleMetricKey or primaryFunnelKey must be present.
primaryFunnelKeystringOptional
The key of the primary funnel group for this experiment. Either primarySingleMetricKey or primaryFunnelKey must be present.
randomizationUnitstringOptional
The unit of randomization for this iteration. Defaults to user.
reallocationFrequencyMillisintegerOptional
The cadence (in milliseconds) to update the allocation.
covariateIdstringOptional
The ID of the covariate CSV
attributeslist of stringsOptional
The attributes that this iteration's results can be sliced by
Response
Iteration response
hypothesisstring
The expected outcome of this experiment
statusenum
The status of the iteration: not_started, running, stopped
createdAtlong
Timestamp of when the iteration was created
_idstringOptional
The iteration ID
startedAtlongOptional
Timestamp of when the iteration started
endedAtlongOptional
Timestamp of when the iteration ended
winningTreatmentIdstringOptional
The ID of the treatment chosen when the experiment stopped
winningReasonstringOptional
The reason you stopped the experiment
canReshuffleTrafficbooleanOptional
Whether the experiment may reassign traffic to different variations when the experiment audience changes (true) or must keep all traffic assigned to its initial variation (false).
flagsmap from strings to objectsOptional
Details on the flag used in this experiment
reallocationFrequencyMillisintegerOptional
The cadence (in milliseconds) to update the allocation. Only present for multi-armed bandits.
versionintegerOptional
The current version that the iteration is on
primaryMetricobjectOptional
Deprecated, use primarySingleMetric and primaryFunnel instead. Details on the primary metric for this experiment.
primarySingleMetricobjectOptional
Details on the primary metric for this experiment
primaryFunnelobjectOptional
Details on the primary funnel group for this experiment
randomizationUnitstringOptional
The unit of randomization for this iteration
attributeslist of stringsOptional
The available attribute filters for this iteration
treatmentslist of objectsOptional
Details on the variations you are testing in the experiment
metricslist of objectsOptional
Details on the metrics for this experiment
layerSnapshotobjectOptional
Snapshot of the layer state on iteration stop, if part of a layer. Otherwise omitted.
covariateInfoobjectOptional
Details of the covariate file for stratified sampling
secondaryMetricslist of objectsOptionalDeprecated
Deprecated, use metrics instead. Details on the secondary metrics for this experiment.