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Randomization

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Randomization

Owned by Melanie Mansuy (Unlicensed)
Last updated: Apr 10, 2025 by Alyssa Hill

Recent upgrades to the REDCap Randomization module allows the following:

  • Automated Randomization: Enhanced automation options based on specified logic or field values.

  • Enhanced User Privileges: More granular control over user rights for setting up, performing, and viewing randomization.

  • Multiple Allocation Tables: Support for multiple allocation tables for complex randomization schemes. Each table must use different, unique randomization fields.

Initial Considerations

Randomization is a process that assigns participants/subjects by chance (rather than by choice) into specific groups. The randomization module in REDCap will help you implement a defined randomization model within your project, allowing you to randomize your subjects.

The module monitors the overall allocation progress and assignment of randomized subjects.

It is strongly recommended that you have your statistician involved in both the project design as well as development of the allocation tables. To get started, watch the in tool video tutorial found in the randomization ‘setup’ page:

 

  • REDCap does NOT create the randomization table(s) for you

    • You will need to create 2 unique allocation tables, one for Development mode (testing) and one for Production Mode

    • Randomization must be setup & tested while your project is in ‘Development’ Mode

  • Your allocation table should be at least 20% larger than your sample size

    • Accommodates drop-out rate and allows for flexibility when needed

  • All projects utilizing REDCap’s Randomization functionality, require ‘BMIC Randomization Review’ call prior to project start.

    • This review is performed to ensure projects are configured adequately before go live, as randomization errors are very difficult to resolve in Production mode!

    • This review can take up to 2 weeks to schedule, please plan accordingly! This must be completed before your project may be approved for Production Mode (in order to collect real data).

    • During the randomization review, be prepared to address the following... (expand below)

  1. Project workflow/operations: Be prepared to present an overview of your project purpose, configuration, # participants, recruitment processes, etc. A screen-share will be hosted to provide BMIC team with a walkthrough through of your project workflow, configuration and user rights set up, etc..

  2. Consent process (as applicable)

  3. Inclusion/Exclusion instrument & criteria: Be prepared to showcase your inclusion criteria and how the data is captured

  4. Randomization Model: Simple, Complex, Blinded, Unblinded, manual, automatic, allocation table numbers, etc.

    1. Randomization field & Safeguards: Be prepared to review the instrument where your randomization field is located and show the safeguards you have in place to ensure the Randomization button only appears when a participant meets all inclusion criteria. This can be accomplished using branching logic.

    2. For example, if your inclusion criteria is that the participant is over 18 and female, then you would create branching logic for your randomize field which hosts logic that enforces the field only be shown when the participant has selected they are over 18 AND female.

  5. User Rights: Which users are allowed which randomization privileges and why

  6. Contingency Plan: If REDCap is ever down, what will you do? Wait to randomize, use envelopes? etc.

Summary of Task(s)

(1) Plan out your randomization model:

  • Will you have a single randomization scheme or multiple?

    • A single scheme is typically adequate for most project’s

  • Which (strata) field(s) and field values will you use in your randomization scheme?

  • Will you randomize by site/group?

  • Will you perform the randomization manually or automatically using a logic trigger?

    • Consider timing of randomization given operational workflow…

      • Will this occur after determining eligibility or perhaps as close to treatment time as possible (to avoid death or withdrawal before treatment starts)?

         

    • Which user(s) will be granted which randomization permission(s)?

       

(2) Create & Upload your ‘Development’ randomization table:

NEVER use the REDCap Template Allocation examples as the allocation tables for your project. They are solely meant to provide examples and NOT to be utilized in a project. 

Your statistician should create your allocation tables in the format of these template tables.

Your table must be generated outside of REDCap using other software (e.g. Excel, SAS, Stata, R). This is usually done by the statistician/data analyst involved in your project. The randomization table must be in .CSV format to be uploaded into REDCap.

  • Once your table is uploaded, REDCap uses the allocation table as a lookup for determining how to randomize the subjects.

 

(3) Test your ‘Development’ table:

  • Test your operational workflow start to finish from all user roles/experiences to ensure configuration and tables work as intended.

(4) Create & Upload your ‘Production’ randomization table:

  • A new allocation table must be used for Production, you may NOT use the same table used in development mode.

(5) Request a randomization review call:

How to Configure REDCap Randomization

Written Process:

  1. Enable the Randomization module

    1. Click "Enable" on the Project Set-Up page under the section Enable Optional Modules & Customizations 

  2. Setup User Rights to ensure you and your staff have access to appropriate privilege based on project requirements.

    1. SETUP: This privilege grants access to the ‘setup’ page where the model/scheme/tables are created/uploaded.

    2. DASHBOARD: This privilege grants access to the overview dashboard which shows what group each record is designated to and how many allocation have been used across all stratas.

    3. RANDOMIZE: This privilege grants access to perform randomize action at the record level.

  3. Return to Project Setup page, click ‘Set Up Randomization’

  4. Setup your Randomization model

    1. Click ‘Add new randomization model’

       

    2. Complete steps (1-3) as applicable, based on your project needs/requirements

      • A) select strat fields

        • add as many fields as needed

      • B) Select group/site

      • C) Choose Randomization field

    3. Save Randomization model

  5. Download example Allocation Tables 

    1. These tables are NOT to be used for your project, but only as a guide to understand how to create your own tables with correctly coded values.

  6. Upload Your Project's Allocation table for the Development testing

    1. Click ‘Choose File’ for use in DEVELOPMENT status

      1. Select desired file

    2. Click ‘Upload File’ to confirm action

      • A new allocation table must be used for Production, you may NOT use the same table used in development mode.

  7. Confirm Trigger Option

    1. Read in-tool explanation and setup as needed for your project

      1. IF using a ‘tigger logic’, provide the desired logic and click ‘Save trigger option’

  8. TEST your project

    1. Use the Record Dashboard to add test records and test your randomization process & setup

    2. As needed, you can edit your randomization model during the development/testing process.

      1. Anytime you edit the model during testing, you will have to…

        1. Click the ‘setup’ action

        2. ‘Erase’ the current model

        3. Setup model as new (including allocation table uploads)

    3. Repeat this process as many times as necessary

  9. After you have fully tested your project, upload your ‘PRODUCTION’ allocation table.

    1. Your Production allocation table MUST be unique and must not be the same as your Development allocation table.

      1. Reminders:

      2. Once your project is in production status, the allocation tables will become locked and unmodifiable.

      3. Be sure to include more assignments in your allocation table than you think you will need (to accommodate possible drop-out and drop-in of subjects).

    2. Navigate to the randomization ‘setup’ page

    3. Click ‘Choose File’ for use in PRODUCTION status

      1. Select desired file

    4. Click ‘Upload File’ to confirm action

  10. Request ‘Move to Production’ / ‘Randomization Review Call’

    • request that your project be moved to Production. Note that you will need to have your Production randomization allocation table uploaded.

    • The BMIC team will coordinate a meeting to review as noted above to ensure. The Prod excel template

 

FAQ’S

What if I need multiple different models in one project, is this possible?

Yes, this is possible!

To do so navigate to the randomization tool, click ‘add new randomization model’ and complete the model setup per normal processes.

NOTE: a unique ‘target’ field is required for each randomization model. Randomization models should never be duplicated.

All randomization model(s) are saved to the ‘summary’ page.

Can I change my randomization model once my project is in Production Mode?

No. You cannot change your randomization model once in production mode.

You can only update the ‘trigger option’ for your models once in production mode.

What if a record is randomized incorrectly?

In the event a randomization error occurs, there may be actions the BMIC, REDCap Admin support team can take to further assist such as appending additional allocations, removing an assignment, etc. There may be re-charge fee required for support.

Note: Performing these actions is typically rare and only done when things have not gone as planned in the project.

If special support is needed, submit a helpdesk ticket with the specific scenario: