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Working with Randomization

REDCap Randomization – Working with & Managing Randomization

Article ID RC-RAND-03 — Working with & Managing Randomization
Domain Randomization
Applies To Study Coordinators and data entry staff (Sections 4–6); REDCap Administrators (Section 7); requires project in Production with a configured randomization model
Prerequisite RC-RAND-01 — Randomization Concepts & Terminology; RC-RAND-02 — Randomization Setup Guide
Version 1.1
Last Updated 2026-05-11
Author See KB-SOURCE-ATTESTATION.md
Related Topics RC-RAND-01 — Randomization Concepts & Terminology; RC-RAND-02 — Randomization Setup Guide; RC-USER-01 — User Rights: Overview & Three-Tier Access; RC-EXPRT-01 — Data Export: Overview & Workflow; RC-ALERT-01 — Alerts & Notifications: Setup

1. Overview

What is this?

This document covers what happens after a randomization model is set up and the project is in production. It is organized by audience: regular users (coordinators, data entry staff) in Sections 4--6, and REDCap administrators in Section 7. Administrators should read both sections.

Why does it matter?

Running and monitoring randomization correctly is as important as setting it up correctly. Errors at this stage — randomizing the wrong record, misreading the dashboard, or an administrator making an unnecessary intervention — can compromise study integrity and require protocol deviations.

2. Learning Objectives

After reviewing this document, the user will be able to:

  • Manually randomize a record using the Randomize button

  • Explain when and how automatic trigger randomization fires

  • Identify what an unauthorized user sees when they encounter the randomization variable

  • Navigate the randomization summary table and interpret its columns

  • Use the randomization dashboard to monitor allocation progress

  • Use randomization smart variables to capture metadata about the randomization event

  • (Administrators) Append allocations to a production table

  • (Administrators) Use allocation-level edit actions and understand when they are appropriate

3. Randomizing a Record

3.1 Manual randomization — Randomize button

This is the default trigger option. The randomization variable field is replaced in the UI by a Randomize button.

State What the user sees
Record not yet randomized A Randomize button appears where the randomization variable field would be.
User clicks Randomize button A confirmation popup appears showing the record and group assignment that will be made. Click the Randomize button in the popup to confirm.
Record successfully randomized (open) The randomization variable shows the assigned group label (e.g., 'Intervention').
Record successfully randomized (blinded) The randomization variable shows an opaque code. The study team cannot determine the group from this value.
Stratification or DAG values missing REDCap displays a prompt listing the missing values before allowing randomization. Complete those fields and retry.

Note: In Development mode, REDCap shows a yellow banner warning not to randomize real participants. This warning does not appear in Production mode.

3.2 Automatic trigger randomization

If the randomization model was configured with one of the two trigger logic options, randomization can fire automatically in addition to (or instead of) the manual button.

Trigger Option When randomization fires automatically
Trigger logic — users with Randomize rights only All three conditions must be true simultaneously: (1) the trigger option is set to this mode, (2) the defined trigger logic evaluates to true, (3) a user with Randomize rights saves the defined instrument/event.
Trigger logic — all users including survey respondents Both conditions must be true: (1) the defined trigger logic evaluates to true, (2) any user saves the form OR a survey respondent completes the survey form. Randomize rights are NOT required to trigger this mode.

Note: Even with automatic triggers configured, a user with Randomize rights can still manually click the Randomize button at any time. A user without Randomize rights will see the field greyed out and non-interactive regardless of trigger mode.

3.3 What unauthorized users see

Users who do not have the Randomize right assigned to their account see the randomization variable as a greyed-out, non-interactive field --- for both open and blinded randomization types. They cannot click the Randomize button or interact with the field in any way. This is by design and is not a bug.

4. Randomization Summary Table

Navigate to Applications → Randomization to see the summary table for all randomization models in the project. Each row is one model.

Column What it shows
# (Order) The sequence in which randomization models were created in this project.
Target The variable name of the randomization variable for this model. If automatic triggers are configured, an expandable option shows the trigger logic.
Allocation type Open randomization: green open envelope icon. Blinded randomization: red closed envelope icon.
Stratification Red X if no stratification. Variable names of all stratification variables if stratification is configured.
Total allocations (Dev / Prod) Two sub-columns showing how many allocation slots have been defined for development mode and production mode respectively.
Setup (icon) Opens the randomization model setup page for review or editing (Development mode only for structural changes).
Dashboard (icon) Opens the randomization dashboard for that model. Requires Dashboard user right.
Randomization ID A system-generated global ID for the model. Primarily used by REDCap administrators for backend database lookups.

5. Randomization Dashboard

The dashboard provides a real-time view of allocation usage for a specific randomization model. Access it via the Dashboard icon in the summary table. Requires the Dashboard user right.

5.1 What all users see

Column What it shows
Grey dot / Green checkmark Grey dot = allocations still available. Green checkmark = all allocations for this row have been assigned. A quick indicator that you are at maximum for a group.
Used Number of allocations assigned to records so far for this row.
Not Used Number of allocations still available for this row.
Allocated records Record IDs of all records assigned to this group. IDs are clickable and navigate directly to that record.
Dynamic columns Additional columns appear based on configuration: DAG column, stratification variable columns, randomization variable column. Headers show field labels and variable names — these differ per project.

Note: Each row in the dashboard represents a unique combination of cohort, DAG, and stratification values (if applicable). A project with 2 cohorts and 2 stratification levels will have 4 rows total (2 cohorts × 2 strata), not 2.

5.2 What administrators additionally see

Administrators see one additional column: View. Clicking the dashboard icon in the View column drills into that specific allocation group and reveals the full allocation table with individual slot-level actions. See Section 7 for administrator actions.

5.3 Monitoring best practices

  • Check 'Not Used' counts regularly: If a group is approaching zero remaining slots, contact your REDCap administrator to append more allocations before they run out.

  • Use the green checkmark as an alert: A checkmark means that group's allocations are exhausted. New records matching that combination will not be randomizable until more slots are added.

  • Record IDs are clickable: Use the dashboard to navigate directly to randomized records for quick auditing.

6. Randomization Smart Variables

REDCap provides three smart variables that capture metadata about the randomization event. These can be piped into fields, alerts, or reports to create an audit trail or trigger downstream logic.

Smart Variable What it returns Notes
[rand-time] Date and time the record was randomized Uses server time (not local device time). If server is in Eastern time and user is in Pacific time, Eastern time is recorded.
[rand-utc-time] Date and time in Coordinated Universal Time (UTC) Use this for cross-timezone consistency or international studies.
[rand-number] The randomization allocation number assigned to the record For blinded randomization: equivalent to piping the randomization field. For open randomization: the randomization number from the allocation table (optional field in table setup).

Note: For projects with multiple randomization models, each smart variable can be targeted to a specific model. Consult the REDCap smart variable documentation within REDCap for the exact syntax.

7. Administrator Options

This section is for REDCap administrators only. Regular users cannot perform these actions. Intervention at the allocation level should be rare — if frequent administrator intervention is needed for a project, the randomization setup should be re-evaluated.

⚠ Warning: All administrator allocation actions require specifying a reason, which is logged. They also require typing 'confirm' to execute. This is intentional — these actions can affect study data integrity.

7.1 Appending allocations to a production table

The most common administrator action. Required when a project runs out of allocation slots in production.

  • Location: Applications → Randomization → Setup icon for the model → Step 3 (Production allocation table) → 'Upload more allocations (Administrators only)' link

  • How it works: Upload a new allocation table file. It appends to the existing table rather than replacing it. For example: 100 existing slots + uploading 100 more = 200 total slots. Can be done as many times as needed, one file at a time.

  • File format: Same format as a regular allocation table. Download a fresh template from the setup page if needed.

7.2 Allocation-level actions (via the View column in the dashboard)

After clicking the dashboard icon in the View column, administrators see the full allocation table with an Edit column. Each unassigned slot has up to four action icons; assigned slots have one.

Action What it does Available for
Remove randomization Removes the randomization assignment from a record, freeing that allocation slot for reassignment to another record. The record returns to an un-randomized state. Assigned slots only
Edit target field Remaps the allocation to a different cohort group. Requires: reason (logged), new value, and typing 'confirm'. Unassigned slots only
Edit target alternate Remaps the randomization group (alternate number). Mostly relevant for blinded randomizations — affects the [rand-number] smart variable but not direct randomization functionality. Requires: reason (logged), new value, and typing 'confirm'. Unassigned slots only
Manual randomization Manually assigns a specific record to this allocation slot. The record must not already be randomized. Requires: reason (logged), valid record ID, and typing 'confirm'. Unassigned slots only
Make sequence unavailable Removes the allocation slot entirely from the pool — it will not be used for any future randomizations. Displayed with a stop symbol. Requires: reason (logged) and typing 'confirm'. Unassigned slots only
Restore availability Reverses a 'Make sequence unavailable' action. Only available on slots previously made unavailable. Requires: reason (logged) and typing 'confirm'. Unavailable slots only

7.3 Redoing a randomization model in production

This scenario should be avoided at all costs. If a randomization model in a production project needs to be rebuilt from scratch, the options are limited and all have significant consequences.

⚠ Warning: Moving a production project back to Development status to erase a randomization model is disabled — even for administrators — through the standard 'Other Functionality' interface. The only paths forward involve backend database manipulation or cloning the project and starting over. Neither is straightforward. This reinforces why thorough testing before production is essential.

8. Questions & Answers

9. Common Mistakes & Gotchas

Confusing the randomization dashboard with project dashboards

  • What happens: User navigates to Applications → Project Dashboards looking for randomization information and finds only their custom data visualizations.

  • Prevention: The randomization dashboard is accessed via Applications → Randomization, then clicking the Dashboard icon for a specific model. It is a separate feature from Project Dashboards.

Not monitoring allocation counts proactively

  • What happens: Allocation slots run out mid-study. New enrollees cannot be randomized. Study operations are disrupted while an administrator locates and appends more allocations.

  • Prevention: Establish a regular cadence for checking the 'Not Used' counts in the dashboard. Build an alert or report that flags when a group drops below a defined threshold (e.g., 20 remaining slots).

Administrator intervening in allocation table without logging the reason properly

  • What happens: An allocation edit is made without a clear reason, creating audit trail gaps that become problematic during regulatory review.

  • Prevention: Always enter a specific, meaningful reason when performing allocation-level actions. REDCap logs these reasons --- treat them as protocol documentation.

Frequent administrator interventions indicating a setup problem

  • What happens: Administrators are regularly asked to correct individual allocations — removing randomizations, remapping groups, manually assigning records. Each intervention is a study integrity risk.

  • Prevention: If administrator interventions are happening frequently for the same project, schedule a review of the randomization setup. The root cause is almost always a design issue: insufficient allocation table size, incorrect stratification setup, or inadequate user training.

11. Version & Change Notes

REDCap Version Notes
15.4.4+ Randomization 2.0: automatic trigger options available. Smart variable behavior and dashboard columns consistent with this document. Verified compatible through REDCap 17.
Pre-15.x Automatic triggers not available. Section 4.2 (automatic trigger behavior) does not apply. Manual-only randomization. Smart variables [rand-time], [rand-utc-time], [rand-number] — verify availability in your version.

REDCap LLM Knowledge Base | RC-RAND-03 — Working with & Managing Randomization | Working with & Managing Randomization