Randomization

Owned by Gillian Javetski
Jan 08, 2025
2 min read

Randomization in CommCare is a powerful feature that enables you to implement randomized workflows, generate random values, and tailor application logic based on random numbers. Below are a few ways that you can leverage randomization properties in CommCare.

Use the Random Function

You can ause the common Random Function (described here: CommCare Functions | random ) to randomize your outputs.

  • Return:  Returns a random number between 0.0 (inclusive) and 1.0 (exclusive). For instance: 0.738  

  • Arguments: None

  • Usage: random()

  • Example Usage: When you need to generate a random number.  For example, to generate a number between 5 and 23, you can use (random()*(23 - 5)) + 5.  This will be something like 12.43334.  You can convert that to a whole number by using int((random()*(23 - 5)) + 5).  You can also reference questions instead of directly typing numbers.  Ex. int(random()*(/data/high_num - /data/low_num) + /data/low_num).  

External Randomization

For projects requiring precise control over randomization, patient groups can be randomized externally and then uploaded to CommCare using the Case Importer tool (Importing Cases Using Excel) . This method is ideal when all participants are registered before randomization.

How to Implement External Randomization

  1. Export Patient Data: After all participants are registered in CommCare, export their case data.

  2. Randomize in Excel or External Tool: Use Excel or a dedicated randomization system to assign patients to groups (e.g., "Treatment" or "Control"). Ensure the assignments follow the required distribution.

  3. Prepare for Import: Add the randomized group assignments to a column in the Excel file. Format the file according to CommCare's Case Importer guidelines, ensuring all required columns (e.g., Case ID) are included.

  4. Upload to CommCare: Use the Case Importer tool in CommCare HQ to upload the updated case data with the group assignments.

  5. Update Study Assignments: The uploaded group assignments will now be available as case properties in CommCare. These properties can be used to guide workflows or reporting.

Example Use Case: An implementing partner randomized patients externally using a statistical tool. During patient intake, when the patient was registered as a mobile worker, the study team entered the assigned study group into a custom user field in CommCare. This ensured that all participants followed the predefined group assignments during the study.

Additional Notes

  • This method is best suited for projects where all participants are registered upfront, as it ensures the correct distribution of participants across groups.

  • For projects with rolling admissions, consider alternative randomization approaches, such as using the random() function or bucketed randomization directly within CommCare.

Display a Random Question

You can set up a form that will display a random yes/no question from a lookup table.  This is useful for asking randomized questions for doing knowledge assessment, or to send random behavior change communication out via messaging.

Read more here: Lookup Tables | Setup a Form to Display a Random Question from Lookup Table

Advanced Randomization Functions

For more advanced randomization functions, check out the CommCare Forum and search for other randomization questions.