cohortid

Cohortid, sometimes written as cohort_id or cohortId, is a unique identifier assigned to a group of individuals who share a defined characteristic or event within a dataset. In analytics and data management, a cohortid enables longitudinal analysis by linking events and attributes across time for members of the same cohort rather than for individuals in isolation.

Cohort identifiers are used to segment data for retention, engagement, and lifecycle analyses. They support comparing behavior across different groups, such as users who signed up in the same week or users who were exposed to a particular feature. They are also used in reporting to calculate metrics like cohort-based retention, revenue per cohort, and among-cohort comparisons in A/B testing.

Formation and storage methods vary. A cohortid can be generated deterministically from a defining attribute (for example, a signup week such as 2024-W15 or a product version), or assigned by an ETL or data processing pipeline. The cohortid is typically stored as a field on user records or events, or in a separate cohorts table that maps cohortid to its defining characteristics (name, start and end dates).

Privacy and governance considerations are important because cohort data can reveal patterns by time or behavior and may be linkable across datasets. Practices include data minimization, pseudonymization or hashing where appropriate, access controls, and compliance with relevant privacy regulations.

Common pitfalls include inconsistent cohort definitions, time zone mismatches, cohort drift over time, and misalignment between data sources. Clear documentation of cohort criteria and refresh cadence helps ensure reliable, reproducible analyses.