View source for Implementing randomization

== Implementing Randomization ==

Implementing [[randomization]] in an RCT involves generating a random allocation sequence and assigning participants to intervention groups while maintaining [[allocation concealment]] and group balance.

=== Step-by-Step Guide ===

=== 1. Define the Randomization Design ===
Choose a randomization strategy based on the trial's objectives, [[sample size]], and structure.

==== Types of Randomization ====

* '''Simple Randomization'''
** Equivalent to flipping a coin for each participant.
** Works well for large sample sizes but may result in imbalance in smaller trials.
** '''Example''': A random number generator assigns participants to Group A or B.

* '''Block Randomization'''
** Ensures balanced group sizes at regular intervals.
** '''Example''': Blocks of 4 (AABB, ABAB, BBAA) randomly assigned to participants.
** Useful for smaller sample sizes.

* '''Stratified Randomization'''
** Ensures balance for important covariates (e.g., age, sex, disease severity).
** Randomization occurs within strata to prevent confounding.

* '''[[Minimization]]'''
** An adaptive method that assigns participants to the group that minimizes imbalance on key variables.
** Particularly useful in small trials.

* '''Cluster Randomization'''
** Randomization occurs at the group level (e.g., clinics, schools) rather than for individual participants.

=== 2. Generate the Randomization Sequence ===

Use secure and validated tools to create a reproducible random sequence.

==== Tools for Random Sequence Generation ====
* Computer software: '''Stata''', '''R''', '''SAS'''
* Online services: '''Sealed Envelope''', '''Random.org'''
* Random number tables (less common)



=== 3. Implement Allocation Concealment ===

Ensure that the allocation sequence is concealed from recruiters and participants to avoid selection bias.

* Centralized randomization (e.g., IWRS, IVRS)
* Sealed, opaque, sequentially numbered envelopes
* Pharmacy-controlled assignment

=== 4. Assign Participants ===

Assign participants to their randomized group only after:
* Confirming eligibility
* Completing baseline assessments

=== 5. Document and Monitor the Process ===

* '''Randomization List''': Keep the allocation sequence securely stored and accessible only to designated staff.
* '''Randomization Log''': Document each assignment while maintaining future allocation concealment.
* '''Quality Control''': Monitor and audit the process to ensure fidelity.

=== Example Workflow for Randomization ===
# Generate a block randomization sequence with [[stratification]] by sex and age.
# Upload the sequence to a centralized online randomization system.
# Upon enrollment, the recruiter logs in, confirms eligibility, and receives the group assignment.
# A blinded pharmacist or coordinator administers the assigned intervention.

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=== Bibliography ===

# Schulz KF, Grimes DA. Generation of allocation sequences in randomised trials: chance, not choice. ''The Lancet''. 2002;359(9305):515–519.
# Moher D, Hopewell S, Schulz KF, et al. [[CONSORT]] 2010 explanation and elaboration: updated guidelines for reporting parallel group randomised trials. ''BMJ''. 2010;340:c869.
# Higgins JPT, Thomas J, Chandler J, et al. (editors). Cochrane Handbook for Systematic Reviews of Interventions, version 6.3 (updated February 2022). Cochrane; 2022. Chapter 8: Methods for sequence generation and allocation concealment.
# Altman DG, Bland JM. Statistics notes: how to randomise. ''BMJ''. 1999;319(7211):703–704.
# Piantadosi S. Clinical Trials: A Methodologic Perspective. 3rd ed. Wiley; 2017. Chapter 7: Randomization methods and implementation.

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''Adapted for educational use. Please cite relevant trial methodology sources when using this material in research or teaching.''