Document a Reproducible Randomization Sequence Safely

Separate reproducibility from access

A reproducible randomization sequence allows an authorized reviewer to reconstruct how assignments were generated. Allocation concealment prevents people enrolling participants from knowing upcoming assignments. These purposes need different access arrangements: reproducibility does not mean posting the live sequence or its reconstructive details in a shared recruitment file.

Start with an approved specification naming the allocation unit, group order, ratio, intended size, strata, and any restrictions. Identify who generates the sequence, who independently checks it, and how assignments are released. A sequence-generation script cannot by itself provide a reliable enrollment workflow.

Record the complete computational recipe

Preserve the script, software and package versions, random-number generator settings, seed or saved state, and input specification in a restricted record. The official R random-number documentation explains seed setting, generator types, and version-related reproducibility. The same seed alone is not a complete computational specification across different algorithms or software behavior.

Generate a practice sequence with fictional labels before producing the operational version. Check that output identifiers are unique, arm labels match the specification, and the expected number of assignments is present. Re-run the complete process in the intended environment and compare the resulting files.

Understand a fictional balance check

Suppose a practice specification requires 12 assignments in a 1:1 ratio with complete balanced blocks of four. Each complete block should contain two A and two B assignments, giving six of each overall. These are fictional structural checks, not a recommendation to reveal fixed small blocks to enrolling staff.

A simple randomization process with probability one-half per assignment does not guarantee six of each in twelve assignments. Do not declare a valid simple-random sequence defective merely because it is imbalanced, and do not repeatedly regenerate it until the balance looks attractive unless a prespecified procedure requires that restriction.

Verify implementation and concealment

Test how the operational system handles duplicate requests, incorrect stratum information, interruptions, and cancellation after assignment. Preserve an audit trail rather than reusing an assignment for another participant without an approved rule. Restrict access to the full sequence and any settings that would allow prediction of future assignments.

The SPIRIT trial-design guidance distinguishes the planned design and ratio from other randomization details. Document those details explicitly instead of using “randomized” as the entire description.

Before enrollment, obtain the study's required independent review of the specification and workflow. Record that review only when it actually occurs. Archive the checked generation package and a file checksum, then maintain assignment logs separately. This guide provides a documentation workflow; it does not certify an operational randomization service or establish that a generated sequence is concealed in practice.

Sources checked on 1 November 2026; practice scenario is fictional.